Ideally, we'd use the tarballs from
http://llvm.org/releases/download.html but I didn't feel like modifying
the script more than I already did to make it work at all (bug 1262735).
The new tarball for Linux was built on
https://tools.taskcluster.net/task-inspector/#LCUn8aEgTBeRJ11a3qTlDQ/0
The new tarball for Mac was built on a loaner, after installing cmake
and ninja, as well as building ld64 127.2 from source because the
installed version would assert while building clang. The latter required
manually adding some missing headers to /usr/include. TSAN was also
disabled because it requires APIs that are not available on the OSX
version on the build slaves (e.g. pthread_introspection_hook_install).
Building clang also required using a mac clang from tooltool, the system
one lacking support for atomics.
Both point to the same path for cc and cxx, but not for gcc_dir, which
makes no sense. That's the only significant difference between both, so
just merge them both, and use the merged file in the taskcluster build
script.
Instead, copy libgcc from the GCC used to build clang at each stage.
When passing --gcc-toolchain, the flag ends up appearing in the output
of llvm-config, and completely defeats the purpose of copying libgcc in
clang/lib/gcc.
Since build-clang.py requires a gcc_dir to be set, and we're using GCC
from there to build clang, we might as well copy libgcc from there
instead of building a fresh GCC. On the taskcluster job building clang,
GCC comes from a tooltool package that is already the result of
build-gcc anyways.
When passing -DCMAKE_C_COMPILER="gcc -flags" to CMake, ninja then tries
to literally call "gcc -flags", not "gcc" "-flags", and a "gcc -flags"
file obviously doesn't exist, so the build fails.
This fixes a regression from bug 1042132. Hopefully, this also doesn't
regress bug 1042132 itself.
