.github: Update the path used for the homebrew LLVM install on macOS

Pull Request: https://github.com/freebsd/freebsd-src/pull/1212

.github: Switch to v4 of actions/checkout

GitHub is emitting a warning that v3 is deprecated due to using
Node.js 16.

.github: Enable manually running github actions

Sponsored by: Arm Ltd

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/878

.github: Build stable/14

Sponsored by: Arm Ltd

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/878

.github: Test DISK_IMAGE_TOOLS_BOOTSTRAP in CI

Building the tools is quick so we should provide coverage of this to
ensure it keeps working, especially on non-FreeBSD.

Reviewed by: emaste, arichardson
Differential Revision: https://reviews.freebsd.org/D39073

.github: Restrict permissions on cross-build jobs.

.github: Switch to v3 of actions/checkout.

GitHub is emitting a warning that v2 is deprecated due to using
Node.js 12.

Reported by: GitHub
Reviewed by: arichardson, emaste
Differential Revision: https://reviews.freebsd.org/D37769

.github: Attempt to fix and increase robustness of macOS action

Homebrew has added LLVM 14 and made that the default version, but GitHub
continues to install LLVM 13 for now, so it ends up only accessible via
the versioned name and not the unversioned one. We also add an explicit
installation of llvm@13 so that, if GitHub updates the image to using
LLVM 14, the action continues to work, albeit slightly more slowly. This
also ensures the compiler label remains correct rather than outdated, as
has occurred in the past, and that we don't get new versions of LLVM
before we're ready for them, which is especially relevant for stable
branches. This all mirrors how the Ubuntu jobs are configured.

.github: Add a build on Ubuntu 22.04 using llvm 14.

Reviewed by: uqs
Pull Request: https://github.com/freebsd/freebsd-src/pull/599

.github: Cross-build aarch64 as well as amd64 kernels.

This required adding an explicit os list to the matrix.

Reviewed by: uqs
Pull Request: https://github.com/freebsd/freebsd-src/pull/599

.github: Update compilers used for cross-build testing.

- Drop clang 9 build, and switch the remaining ubuntu build to
the more modern clang 12.

- Update the label for the macos-latest builds which are now using
clang 13 rather than clang 12.

Reviewed by: uqs
Pull Request: https://github.com/freebsd/freebsd-src/pull/599

Make it clear we're running clang-12 for the GH actions

This chases a homebrew change in the default clang version.

Reviewed by: arichardson
Differential Revision: https://reviews.freebsd.org/D31231

.github: Attempt to un-break Clang 9 action

GitHub removed Clang 9 from the 20.04 image[1], breaking this build.
Thus, manually add the specific versioned packages we need for the
Ubuntu jobs to ensure they're installed. Note that we don't do the same
for macOS, as Homebrew does not allow multiple llvm@N to co-exist,
giving an error if you attempt to install a second one. In practice we
don't actually use the compiler field here for anything other than the
build name, it's only the cross-bindir that matters, so when it
eventually moves to 12 the name will get confusing but the job will
still work.

MFC after: immediately

[1] https://github.com/actions/virtual-environments/commit/15a610677be406d250c1f6732b03c8b87e693a0a

Enable GitHub actions CI for stable/13 as well

All cross-building patches have been merged to stable/13 so it should
also build fine on macOS+Linux.

Reviewed By: uqs
MFC after: immediately
Differential Revision: https://reviews.freebsd.org/D29831

GitHub actions: unbreak macOS build

Error: llvm 11.0.0 is already installed

Also make the linking failure non-fatal:

Error: The `brew link` step did not complete successfully

Github actions: s/master/main/ for the CI workflow

GH Actions: Use pre-installed clang packages

Also fix the run by setting up the environment in non-deprecated way.

Always run with --debug to understand better what sort of stuff is happening in
the background. Also split out the bmake bootstrap stage (takes about 31s on
ubuntu, but 1m14 on macOS?)

Drops the dependency on coreutils (realpath, nproc) and thus (?) fixes macOS to
be just as fast (4 logical cores vs 2 physical cores before, go figure.)

Reviewed by: arichardson

Add github CI for testing cross-building from Linux and macOS

This builds the kernel-toolchain target and an amd64 GENERIC kernel on
Ubuntu 18.04, 20.04 and the latest macOS to ensure that new changes
don't regress building on non-FreeBSD hosts.

Reviewed By: emaste, lwhsu
Differential Revision: https://reviews.freebsd.org/D26512