Fix llvm-libunwind userspace build on ARM
GCC's libgcc exports a few ARM-specific symbols for ARM EABI, AEABI, or
EHABI or whatever it's called. Export the same ones from LLVM-libunwind's
libgcc_s, on ARM. As part of this, convert libgcc_s from a direct
Version.map to one constructed from component Symbol.map files. This allows
the ARM-specific Symbol.map to be included only on ARM.
Fix ARM-only oddities in struct name/aliases in LLVM-libunwind to match
non-ARM definitions and ARM-specific expectations in libcxxrt /
libcompiler_rt.
No functional change intended for non-ARM architectures.
This commit does not actually flip the switch for ARM defaults from libgcc
to llvm-libunwind, but makes it possible (to compile, anyway).
master 2e10b7a39b9, the last commit before the llvmorg-12-init tag, from
which release/11.x was branched.
Note that for now, I rolled back all our local changes to make merging
easier, and I will reapply the still-relevant ones after updating to
11.0.0-rc1.
The patch is untested and is almost certainly insufficient. Per the
author's request, revert until someone with access to sparc64 hardware
can test and report.
sparc64 is the only architecture currently using the DWARF unwinder from
GCC 4.2.1. Old GCC and related libraries are being removed soon; absent
other changes sparc64 would be left with no unwinder when that happens.
Instead, commit these changes which should at least allow the LLVM
unwinder to build. Someone with access to the obolete sparc64 hardware
supported by FreeBSD will need to test the result.
PR: 233405
Submitted by: cem
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.
