Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Enable -ftrivial-auto-var-init flags for gcc >= 12

Now that gcc >= 12 supports -ftrivial-auto-var-init, add it to
bsd.compiler.mk's "init-all" feature.

PR: 271047
Reviewed by: emaste
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D40208

bsd.compiler.mk: Add a c++20 compiler feature.

This is enabled for clang versions 10+ and GCC versions 10+.

Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D36892

Remove more quotes around Makefile .error/.warn/.info strings.

Reviewed by: imp, emaste
Differential Revision: https://reviews.freebsd.org/D34175

Add an arm64 sha512 feature check

This is only available in recent toolchains. Check for it so we can
use it in libmd.

Reviewed by: emaste
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D33166

bsd.compiler.mk: Fix cross-building from non-FreeBSD

On non-FreeBSD, the various MACHINE variables for the host when
bootstrapping can be missing or not match FreeBSD's naming, causing
bsd.endian.mk to be unable to infer the endianness. Work around this by
assuming it's unsupported.

Note that we can't check BOOTSTRAPPING here as Makefile.inc1 includes
bsd.compiler.mk before that is set, and so we are unable to catch errors
during buildworld itself when cross-building and bsd.endian.mk failed,
but such errors should also show up when building on FreeBSD.

Fixes: 47363e99d3d3 ("Enable compressed debug on little-endian targets")

Enable compressed debug on little-endian targets

Compressed debug was enabled by default in commit c910570e7573, but
broke the build on big-endian targets, and so was disabled in
89ed2ecb14ce.

Older versions of LLD fail with big-endian compressed debug sections.
This was fixed in LLD upstream (commit c6ebc651b6fa) and merged to
FreeBSD main (commit d69d07569ee2) by dim.

External toolchains (e.g. the llvm12 package) will not yet have the fix.
These may be used to link against base system .a archives, so compressed
debug sections would cause trouble even though the base system is fixed.

Enable compressed debug sections again, for little-endian targets only.
As discussed on freebsd-hackers[1] I expect to undo this in the future
(using compressed debug everywhere), once fixed versions of lld are
widely available.

Note that to be pedantically correct we should check both the compiler
and the linker for compressed debug support, but given the external
toolchain constraint the extra complexity does not seem worthwhile.

[1] https://lists.freebsd.org/archives/freebsd-hackers/2021-August/000188.html

PR: 257638
Reported by: jrtc27 [impact of .a archives]
Discussed with: imp
Relnotes: Yes
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D31454

Revert "Disable compressed debug by default"

This reverts commit 89ed2ecb14ceabc27883282cf96559a9e7d52717.

Use compressed debug in standalone userland debug files by default

The compiler supports CFLAGS=-gz=zlib to compress .debug sections in
object files, libraries, and binaries. Enable it to reduce disk usage
for standalone debug files (and /usr/obj).

Reviewed by: dim, kevans
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D29002

bsd.compiler.mk: Use CCACHE_PKG_PREFIX as ports now supports.

bsd.compiler.mk: detect Apple Clang for cross-builds

Apple clang uses a different versioning scheme, so if we enable or
disable certain warnings for Clang 11+, those might not be supported
in Apple Clang 11+. This adds 'apple-clang' to COMPILER_FEATURES, so that
bootstrap tools Makefiles can avoid warnings on macOS.

Reviewed By: imp
Differential Revision: https://reviews.freebsd.org/D29680

Add fileprefixmap compiler feature

-ffile-prefix-map=<old>=<new> is a compiler feature first added in
GCC 8, and implemented for clang 10. It remaps old paths to new paths
in both debug information and __FILE__ and __BASE_FILE__ macros. It can
be used to improve reproducibility or to hide local system directories.

I intend to use it to replace the real source directory and real object
directory with constant values across all builds.

Reviewed by: brooks
Differential Revision: https://reviews.freebsd.org/D28632

bsd.compiler.mk: Detect distribution-provided GCC when executed as cc

Clang always prints "clang $VERSION" regardless of the name used to
execute it, whereas GCC prints "$progname $VERSION", meaning if CC is
set to cc and cc is GCC it will print "cc $VERSION". We are able to
detect some of those cases since it then prints "($PKGVERSION)", where
the default is "GCC", but many distributions override that to print
their name and the package version number (e.g. "Debian 10.2.1-6"), so
nothing tells us it's GCC other than the fact that it's not Clang (and
that there's an FSF copyright disclaimer).

However, GCC's -v option will always print "gcc version $VERSION", so
fall back on using that to detect GCC. Whilst Clang also supports this
option, we should never get here, so Clang handling is not added.

Reviewed by: brooks, emaste, arichardson
Differential Revision: https://reviews.freebsd.org/D28315

Support initializing stack variables on function entry

There are two options:
- WITH_INIT_ALL_ZERO: Zero all variables on the stack.
- WITH_INIT_ALL_PATTERN: Initialize variables with well-defined patterns.

The exact pattern are a compiler implementation detail and vary by type.
They are somewhat documented in the LLVM commit message:
https://reviews.llvm.org/rL349442
I've used WITH_INIT_ALL_* to match Microsoft's InitAll feature rather
than naming them after the LLVM specific compiler flags.

In a range of consumer products, options like these are used in
both debug and production builds with debugs builds using patterns
(intended to provoke crashes on use of uninitialized values) and
production using zeros (deemed more likely to lead to harmless
misbehavior or NULL-pointer dereferences).

Reviewed by: emaste
Obtained from: CheriBSD
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D27131

Avoid recomputing COMPILER_/LINKER_ variables when set explicitly

I noticed that when we build libraries for a different ABI (in CheriBSD) we
were calling ${XCC}/${LD} --version for every directory. It turns out that
this was caused by bsd.compat.mk explicitly setting (X_)COMPILER variables
for that build stage and this stops the _can_export logic from working.
To fix this, we change the check to only set _can_export=no if the variable
is set and it is set to a different value than the cached value.
This noticeably speeds up the tree walk while building compat libraries.
During an upstream amd64 buildworld this also removes 8 --version calls.

Obtained from: CheriBSD
Reviewed By: brooks, emaste
Differential Revision: https://reviews.freebsd.org/D25986

Remove tests for obsolete compilers in the build system

Assume gcc is at least 6.4, the oldest xtoolchain in the ports tree.
Assume clang is at least 6, which was in 11.2-RELEASE. Drop conditions
for older compilers.

Reviewed by: imp (earlier version), emaste, jhb
MFC after: 2 weeks
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D24802

Fix compilation with upstream clang builtin headers.

By using -nobuiltininc and adding the clang builtin headers resource dir
to the end of the compiler header search path, we can still find headers
such as immintrin.h but find the FreeBSD version of stddef.h/stdarg.h/..
first.

This is a workaround until we are able to settle on and complete a plan
to harmonize guard macros with LLVM. We've mostly worked out this on
FreeBSD systems by removing select headers from the installed set of
devel/llvm*, but that isn't a good solution for cross build.

Submitted by: arichardson
Obtained from: CheriBSD
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D17002

Use __ as the separator for the exported vars in bsd.compiler/linker.mk

By using '__' instead of '.' as the separator we can also support systems
that use dash as /bin/sh (it's the default shell on Ubuntu/Debian). Dash
will unset any environment variables that use a non alphanumeric+undedscore
character and therefore submakes will fail to import the COMPILER_*
variables if we use '.' as the separator.

Reviewed By: emaste
Differential Revision: https://reviews.freebsd.org/D22381

Allow for compiler versions >= 10

Both clang and gcc development branches have reached version 10. Since we
only parse for a single digit in the major version number, this causes
COMPILER_VERSION to be set to its default of 0.0.0, meaning version checks
fail with these newer compilers.

Reviewed by: emaste
Approved by: markj (mentor)
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D21413

Add c++14 and c++17 to COMPILER_FEATURES

This will be used to gate the fusefs tests. It's a partial merge of r348281
from projects/fuse2.

Reviewed by: kib, emaste
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21044

fusefs: misc build fixes

* Only build the tests on platforms with C++14 support
* Fix an undefined symbol error on lint builds
* Remove an unused function: fiov_clear

Sponsored by: The FreeBSD Foundation

Don't run cc --version during cleandir/obj stages

This will no work when there is no cc in $PATH (which is the case before the
cross-tools stage once we no longer inherit $PATH in $WMAKE).
The variables set by bsd.compiler.mk/bsd.linker.mk are not needed in these
stages so this avoids a little bit of makefile parsing.

Reviewed By: emaste
Approved By: jhb (mentor)
Differential Revision: https://reviews.freebsd.org/D16814

Only compute the X_COMPILER_*/X_LINKER_* variables when needed

When building CheriBSD we have to set XLD/XCC/XCFLAGS on the command line.
This triggers the $XCC != $CC case in bsd.compiler.mk (and the same for LD
in bsd.linker.mk) which causes it to call ${XCC} --version and
${XLD} --version (plus various awk+sed+echo calls) in every subdirectory.
For incremental builds and stages that only walk the source tree this is
often the majority of the time spent in that directory.

By only computing the value of the X_COMPILER_*/X_LINKER_* variables if
_WANT_TOOLCHAIN_CROSS_VARS is set we can reduce the number of cc/ld calls
to once per build stage instead of once per recursive make.

With this change (and no changes to the sources) the `make includes` stage
now takes 28 seconds at -j1 instead of 86 seconds.

Approved By: brooks (mentor)
Differential Revision: https://reviews.freebsd.org/D17046

CCACHE_BUILD: Avoid ccache when looking up compiler metadata.

MFC after: 2 weeks
Sponsored by: Dell EMC

Reduce exec and fstat overhead for non-build targets.

This is mostly targetting 'make showconfig' and 'make test-system-*' for
the benefit of makeman and universe-one-clang work.

Sponsored by: Dell EMC

Add WITH_SYSTEM_LINKER, on by default, that avoids building lld when possible.

This works similar to WITH_SYSTEM_COMPILER added in r300354. It only
supports lld via WITH_LLD_BOOTSTRAP.

When both SYSTEM_COMPILER and SYSTEM_LINKER logic passes then libclang
will not build in cross-tools. If either check fails though then
libclang is built.

The .info is reworked to notify when libclang will be built since if
either clang or lld needs to be rebuilt, but not the other, the
notification can lead to confusion on why "clang is building".

-fuse-ld= is not used with this method so some combinations of compiler
and linker are expected to fail.

A new 'make test-system-linker' target is added to see the logic results.

Makefile.inc1:
CROSS_BINUTILS_PREFIX support had to be moved higher up so that XLD
could be set and MK_LLD_BOOTSTRAP disabled before checking SYSTEM_LINKER
logic as done with SYSTEM_COMPILER. This also required moving where
bsd.linker.mk was read since XLD needs to be set before parsing it. This
creates a situation where src.opts.mk can not test LINKER_FEATURES or
add LLD_BOOTSTAP to BROKEN_OPTIONS.

Reviewed by: emaste (earlier version)
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D15894

Recognize the base/gcc compiler as GCC.

The existing patterns for 'cc --version' output do not work for GCC
built from the base/gcc port.

Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D15357

add retpoline compiler and linker feature flags

These features indicate that the compiler and linker support the
retpoline speculative execution vulnerability (CVE-2017-5715)
mitigation.

Reviewed by: dim, imp
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D14228

CCACHE_BUILD: Follow-up r321880: Fix some PATH issues with buildworld.

- bsd.compiler.mk: Must ensure that the CCACHE_WRAPPER_PATH comes first
in PATH.
- Makefile.inc1: Must prepend the CCACHE_WRAPPER_PATH into BPATH as it
overrides the PATH set in bsd.compiler.mk in sub-makes. The PATH
set in bsd.compiler.mk is not exported and doing so would cause it to
then override the BPATH set from environment. The only sane solution
is to prepend into BPATH as needed.
CCACHE_PATH could possibly be used for some of this as well.

Sponsored by: Dell EMC Isilon

CCACHE_BUILD: Allow setting CCACHE_BUILD_TYPE=wrapper.

This uses the /usr/local/libexec/ccache/<cc,c++> wrappers rather than
modifying CC to be '/usr/local/bin/ccache cc'. Some forms of compilation
do not support the 'command' type.

Sponsored by: Dell EMC Isilon

Add basic bsd.linker.mk auto included from bsd.compiler.mk.

This will provide LINKER_TYPE and LINKER_VERSION.

MFC after: 2 weeks
Reviewed by: emaste
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D11308

Fix spelling error.

Reported by: arc
Sponsored by: Dell EMC Isilon

Detect clang on macOS. The version string is slightly different.

WITH_CCACHE_BUILD + WITH_META_MODE: Ignore ccache changes.

Ccache will not affect the output of the objects, so just ignore it for
meta mode handling. This avoids having everything rebuild if ccache is
updated.

Sponsored by: EMC / Isilon Storage Division

GCC External: Revert r300886, r300904, r300917, r300918

The fix in r300873 is mostly enough. A fix for lib32 will be
committed.separately.

Always export X_* vars.

This fixes CROSS_TOOLCHAIN builds after r300886 since it
relies on X_COMPILER_TYPE being set.

The X_* vars will only represent the external compiler
being used.

Sponsored by: EMC / Isilon Storage Division

Use sed(1) to determine cc version rather than tail(1) since it is already in ITOOLS.

This fixes 'tail: not found' warnings in installworld after r300351.

Sponsored by: EMC / Isilon Storage Division

Fetch the __FreeBSD_cc_version as COMPILER_FREEBSD_VERSION.

Reviewed by: brooks, bapt, dim
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D6356

Auto determine X_COMPILER_TYPE/X_COMPILER_VERSION if XCC is set.

Reviewed by: brooks, bapt
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D6355

CCACHE_BUILD+META_MODE: Lookup and canonicalize the default CCACHE_DIR.

This is done to prevent not having CCACHE_DIR causing meta mode with filemon to
see stat changes in the ccache dir and cause rebuilds.

Sponsored by: EMC / Isilon Storage Division

For determining the compiler version, quote the string to be echo'd,
otherwise the command might fail. This is because clang -v now results
in the following:

FreeBSD clang version 3.8.0 (trunk 256633) (based on LLVM 3.8.0svn)

The second "3.8.8svn)" string tripped up the shell command.

CCACHE_BUILD: Only export CCACHE_PATH= if it was already set with a value.

Older ccache don't work with an empty CCACHE_PATH value. They will error with:
ccache: FATAL: Could not find compiler "cc" in PATH
make: "/mnt/bdrewery/git/onefs/src/share/mk/bsd.compiler.mk" line 134: Unable to determine compiler type for /usr/local/bin/ccache cc. Consider setting COMPILER_TYPE.

Sponsored by: EMC / Isilon Storage Division

Fix some makeman issues.

- Don't bother looking up REVISION/BRANCH/etc from release/, or the
CPUTYPE check, as these are not used for makeman and wastes time. The also
invokes auto.obj.mk after I reverted auto.obj.mk ignoring -V in r291312.
- Don't modify CC or PATH when WITH_CCACHE_BUILD or WITH_META_MODE is enabled
as it leads to bsd.compiler.mk errors.

Sponsored by: EMC / Isilon Storage Division

Add built-in ccache build support via WITH_CCACHE_BUILD option.

ccache is mostly beneficial for frequent builds where -DNO_CLEAN is not
used to achieve a safe pseudo-incremental build. This is explained in
more detail upstream [1] [2]. It incurs about a 20%-28% hit to populate the
cache, but with a full cache saves 30-50% in build times. When combined with
the WITH_FAST_DEPEND feature it saves up to 65% since ccache does cache the
resulting dependency file, which it does not do when using mkdep(1)/'CC
-E'. Stats are provided at the end of this message.

This removes the need to modify /etc/make.conf with the CC:= and CXX:=
lines which conflicted with external compiler support [3] (causing the
bootstrap compiler to not be built which lead to obscure failures [4]),
incorrectly invoked ccache in various stages, required CCACHE_CPP2 to avoid
Clang errors with parenthesis, and did not work with META_MODE.

The option name was picked to match the existing option in ports. This
feature is available for both in-src and out-of-src builds that use
/usr/share/mk.

Linking, assembly compiles, and pre-processing avoid using ccache since it is
only overhead. ccache does nothing special in these modes, although there is
no harm in calling it for them.

CCACHE_COMPILERCHECK is set to 'content' when using the in-tree bootstrap
compiler to hash the content of the compiler binary to determine if it
should be a cache miss. For external compilers the 'mtime' option is used
as it is more efficient and likely to be correct. Future work may optimize the
'content' check using the same checks as whether a bootstrap compiler is needed
to be built.

The CCACHE_CPP2 pessimization is currently default in our devel/ccache
port due to Clang requiring it. Clang's -Wparentheses-equality,
-Wtautological-compare, and -Wself-assign warnings do not mix well with
compiling already-pre-processed code that may have expanded macros that
trigger the warnings. GCC has so far not had this issue so it is allowed to
disable the CCACHE_CPP2 default in our port.

Sharing a cache between multiple checkouts, or systems, is explained in
the ccache manual. Sharing a cache over NFS would likely not be worth
it, but syncing cache directories between systems may be useful for an
organization. There is also a memcached backend available [5]. Due to using
an object directory outside of the source directory though you will need to
ensure that both are in the same prefix and all users use the same layout. A
possible working layout is as follows:
Source: /some/prefix/src1
Source: /some/prefix/src2
Source: /some/prefix/src3
Objdir: /some/prefix/obj
Environment: CCACHE_BASEDIR='${SRCTOP:H}' MAKEOBJDIRPREFIX='${SRCTOP:H}/obj'
This will use src*/../obj as the MAKEOBJDIRPREFIX and tells ccache to replace
all absolute paths to be relative. Using something like this is required due
to -I and -o flags containing both SRC and OBJDIR absolute paths that ccache
adds into its hash for the object without CCACHE_BASEDIR.

distcc can be hooked into by setting CCACHE_PREFIX=/usr/local/bin/distcc.
I have not personally tested this and assume it will not mix well with
using the bootstrap compiler.

The cache from buildworld can be reused in a subdir by first running
'make buildenv' (from r290424).

Note that the cache is currently different depending on whether -j is
used or not due to ccache enabling -fdiagnostics-color automatically if
stderr is a TTY, which bmake only does if not using -j.

The system I used for testing was:
WITNESS
Build options: -j20 WITH_LLDB=yes WITH_DEBUG_FILES=yes WITH_CCACHE_BUILD=yes
DISK: ZFS 3-way mirror with very slow disks using SSD l2arc/log.
The arc was fully populated with src tree files and ccache objects.
RAM: 76GiB
CPU: Intel(R) Xeon(R) CPU L5520 @2.27GHz
2 package(s) x 4 core(s) x 2 SMT threads = hw.ncpu=16

The WITH_FAST_DEPEND feature was used for comparison here as well to show
the dramatic time savings with a full cache.

buildworld:
x buildworld-before
+ buildworld-ccache-empty
* buildworld-ccache-full
% buildworld-ccache-full-fastdep
# buildworld-fastdep
+-------------------------------------------------------------------------------+
|% * # +|
|% * # +|
|% * # xxx +|
| |A |
| A|
| A |
|A |
| A |
+-------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 3 3744.13 3794.31 3752.25 3763.5633 26.935139
+ 3 4519 4525.04 4520.73 4521.59 3.1104823
Difference at 95.0% confidence
758.027 +/- 43.4565
20.1412% +/- 1.15466%
(Student's t, pooled s = 19.1726)
* 3 1823.08 1827.2 1825.62 1825.3 2.0785572
Difference at 95.0% confidence
-1938.26 +/- 43.298
-51.5007% +/- 1.15045%
(Student's t, pooled s = 19.1026)
% 3 1266.96 1279.37 1270.47 1272.2667 6.3971113
Difference at 95.0% confidence
-2491.3 +/- 44.3704
-66.1952% +/- 1.17895%
(Student's t, pooled s = 19.5758)
# 3 3153.34 3155.16 3154.2 3154.2333 0.91045776
Difference at 95.0% confidence
-609.33 +/- 43.1943
-16.1902% +/- 1.1477%
(Student's t, pooled s = 19.0569)

buildkernel:
x buildkernel-before
+ buildkernel-ccache-empty
* buildkernel-ccache-empty-fastdep
% buildkernel-ccache-full
# buildkernel-ccache-full-fastdep
@ buildkernel-fastdep
+-------------------------------------------------------------------------------+
|# @ % * |
|# @ % * x + |
|# @ % * xx ++|
| MA |
| MA|
| A |
| A |
|A |
| A |
+-------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 3 571.57 573.94 571.79 572.43333 1.3094401
+ 3 727.97 731.91 728.06 729.31333 2.2492295
Difference at 95.0% confidence
156.88 +/- 4.17129
27.4058% +/- 0.728695%
(Student's t, pooled s = 1.84034)
* 3 527.1 528.29 528.08 527.82333 0.63516402
Difference at 95.0% confidence
-44.61 +/- 2.33254
-7.79305% +/- 0.407478%
(Student's t, pooled s = 1.02909)
% 3 400.4 401.05 400.62 400.69 0.3306055
Difference at 95.0% confidence
-171.743 +/- 2.16453
-30.0023% +/- 0.378128%
(Student's t, pooled s = 0.954969)
# 3 201.94 203.34 202.28 202.52 0.73020545
Difference at 95.0% confidence
-369.913 +/- 2.40293
-64.6212% +/- 0.419774%
(Student's t, pooled s = 1.06015)
@ 3 369.12 370.57 369.3 369.66333 0.79033748
Difference at 95.0% confidence
-202.77 +/- 2.45131
-35.4225% +/- 0.428227%
(Student's t, pooled s = 1.0815)

[1] https://ccache.samba.org/performance.html
[2] http://www.mail-archive.com/ccache@lists.samba.org/msg00576.html
[3] https://reviews.freebsd.org/D3484
[5] https://github.com/jrosdahl/ccache/pull/30

PR: 182944 [4]
MFC after: 3 weeks
Sponsored by: EMC / Isilon Storage Division
Relnotes: yes

Don't hide stderr when checking ${CC} --version.

This can have important debugging information such as 'cc: not found' or
'ccache: error: Could not find compiler "cc" in PATH'.

MFC after: 2 weeks
Sponsored by: EMC / Isilon Storage Division

Improve safety of caching from r289659 by only importing of none of the
variables are already set. This should cover odd cases such as the
COMPILER_TYPE override in lib/csu/powerpc64.

X-MFC-With: r289659
MFC after: 3 weeks
Sponsored by: EMC / Isilon Storage Division

Pass COMPILER_TYPE and COMPILER_VERSION to sub-makes to avoid redundant
lookups.

This uses a special variable name based on a hash of ${CC}, ${PATH}, and
${MACHINE} to ensure that a cached value is not used if any of these
values changes to use a new compiler.

Before this there were 34,620 fork/exec from bsd.compiler.mk during a buildworld.
After this there are 608. More improvement is needed to cache a value from
the top-level before descending into subdirs in the various build phases.

Reviewed by: brooks (earlier version)
MFC after: 3 weeks
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D3898

Mention what 'common' is for

The previous commit should have been a logical or not a logical "and"

Pointyhat to: me

${CC} --version doesn't need to be queried if both COMPILER_TYPE and
COMPILER_VERSION are known

Fix typos in comments and wrap to <80 columns

MFC after: 3 days

When using an external toolchain note that gcc 4.8+ supports C++11

Submitted by: imp

Allow CC to not actually exist. During the ports INDEX run, all the
Makefiles are evaluated without building things. In a normal build,
the prerequisites would be built, and CC would be an actual thing. In
an INDEX build, though, they don't exists. Redirect stderr to get rid
of annoying messages, and assume that the compiler version is 0 if the
actual compiler can't tell us. Do this in preference to guessing based
on numbers because gcc410 might be 4.10, or 4.1.0 and without
carefully crafted special knowledge we differentiate between them
easily (also ming-gcc has no clues at all). Elsewhere, don't trust
the compiler version if it is 0.

Support, to the extent we generate proper command lines, compiling
with clang 3.3. Useful for test building -current on a -stable system
in individual directories. Potentially useful if we ever want to
support, say, gcc 4.8 or 4.9's new warnings when building with an
external toolchain (but such support not yet committed). Document
the bsd.compiler.mk interface.

bsd.compiler.mk was implicitly included by bsd.own.mk in historical
versions. With its movement to src.opts.mk, bsd.prog.mk was testing
COMPILER_TYPE without including the bsd.compiler.mk anymore. In the
source tree, this caused no problems, for reasons that aren't clear,
but does cause problems outside of the source tree. Allow
bsd.compiler.mk to be included multiple times safely, and always
include bsd.compiler.mk at the top of bsd.prog.mk. Resist the urge to
put it in bsd.init.mk, since that would reintroduce the implicit
include.

Some warnings depened on the version of clang, allow us to check.

Reviewed by: obrien

Avoid errors when MACHINE is a pseudo machine like "common".

Provide slightly more helpful feedback when we can't figure out what
compiler the user is using.

PR: misc/173914

Fix typo in bsd.compiler.mk.

Allow CC to be gcc46 or similar by matching gcc*.

Don't test the value of the :M matches, either the string matches or does
not.

Add a COMPILER_FEATURES variable that is set in bsd.compiler.mk.

When the compiler is clang add c++11 to COMPILER_FEATURES.

When the compiler supports c++11, default to building libc++. This will
not impact the compliation of programs, but will make it easier for
users with clang compiled systems to test libc++ by passing -stdlib=libc++
to their c++ compliations.

Introduce a new make variable COMPILER_TYPE that specifies what
type of compiler is being used (currently clang or gcc). COMPILER_TYPE
is set in the new bsd.compiler.mk file based on the value of the CC
variable or, should it prove informative, by running ${CC} --version
and examining the output.

To avoid negative performance impacts in the default case and correct
value for COMPILER_TYPE type is determined and passed in the environment
of submake instances while building world.

Replace adhoc attempts at determining the compiler type by examining
CC or MK_CLANG_IS_CC with checks of COMPILER_TYPE. This eliminates
bootstrapping complications when first setting WITH_CLANG_IS_CC.

Sponsored by: DARPA, AFRL
Reviewed by: Yamaya Takashi <yamayan@kbh.biglobe.ne.jp>, imp, linimon
(with some modifications post review)
MFC after: 2 weeks