Remove $FreeBSD$: one-line sh pattern

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

Disable PIE for powerpc bootloaders.

Bootloaders for powerpc are not built as position independent
code. Since bsd.prog.mk is used for building, when PIE is enabled,
the PIE flags are added and that causes the build to fail.
Adding MK_PIE=no stops bsd.prog.mk from adding PIE specific flags.

Submitted by: Dawid Gorecki <dgr@semihalf.com>
Reviewed by: emaste
Obtained from: Semihalf
Sponsored by: Stormshield
Differential Revision: https://reviews.freebsd.org/D28893

[PowerPC] Set fixed boot1.elf load address

Due to the way claiming works, we need to ensure on AIM OFW machines that
we don't have overlapping ranges on any step of the load.

Load boot1.elf at 0x38000 so it will not overlap with anything even if the
entire PReP partition gets loaded by OFW.

Tested on an iBook G4, a PowerBook G4, a PowerMac G5, and qemu pseries.
(qemu pseries is broken without this patch due to the high address used
by lld10.)

Reviewed by: adalava
Sponsored by: Tag1 Consulting, Inc.
Differential Revision: https://reviews.freebsd.org/D24623

Centralize several variables.

MK_CTF, MK_SSP, MK_PROFILE, NO_PIC, and INTERNALLIB are always the
same, so set them in defs.mk. MAN= is common, so set it here too.
This removes a lot of boring repetition from the Makefiles that added
almost no value.

Cleanup CFALGS usage here

Only define the CFLAGS we need.
SSP_CFLAGS is now defined globally, no need to define it here.
Define -D_STANDALONE globally for src/stand builds.

Sponsored by: Netflix

Remove stale dependency on ufsread.c

Remove the now-useless dependency on ufsread.c. In some cases, it was
on the wrong file. But in all cases, we now automatically generate
.depend files, so we don't need it explicitly.

Sponsored by: Netflix

Move some more common stuff up to Makefile.inc. In particular, the no
simd / no float stuff is centeralized here. Also centralise
-ffreestanding since it is specified everywhere.

This, along with a change to share/mk/bsd.cpu.mk to include -mno-avx2
in CFLAGS_NO_SIMD should fix building for newer machines (eg with
CPUTYPE=haswell) where clang was generating avx2 instructions.

Sponsored by: Netflix

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix