Remove $FreeBSD$: one-line sh pattern

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

Move LIBADD lines from usr.bin/clang/*/Makefile one level up

Some utilities under usr.bin/clang were only linked to libz, while most
others were linked to libz and libzstd. Make this consistent, and remove
repetition, by moving these LIBADD lines to usr.bin/clang/clang.prog.mk
and usr.bin/clang/clang.prog.mk.

MFC after: 3 days

Merge llvm-project main llvmorg-16-init-18548-gb0daacf58f41

This updates llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and
openmp to llvmorg-16-init-18548-gb0daacf58f41.

PR: 271047
MFC after: 1 month

Move all sources from the llvm project into contrib/llvm-project.

This uses the new layout of the upstream repository, which was recently
migrated to GitHub, and converted into a "monorepo". That is, most of
the earlier separate sub-projects with their own branches and tags were
consolidated into one top-level directory, and are now branched and
tagged together.

Updating the vendor area to match this layout is next.

Add new llvm-{cxxfilt,lto2,modextract,xray} tools.

Move all sources from the llvm project into contrib/llvm-project.

This uses the new layout of the upstream repository, which was recently
migrated to GitHub, and converted into a "monorepo". That is, most of
the earlier separate sub-projects with their own branches and tags were
consolidated into one top-level directory, and are now branched and
tagged together.

Updating the vendor area to match this layout is next.

Add new llvm-{cxxfilt,lto2,modextract,xray} tools.