tree 9d716ef4aa778de9a28e3a93f247973939b7348e
parent 29eecb56c5f0f26b4751ec9eb79954412fb2991c
author Marcel Hlopko <hlopko@google.com> 1562309914 -0700
committer Copybara-Service <copybara-worker@google.com> 1562309971 -0700

Pass absolute path to gold when using Clang

Prior to this change Bazel's C++ toolchain autoconfiguration generated
toolchain that passed `-fuse-ld=gold` when gold linker was detected.
After this change this will be `-fuse-ld=/usr/bin/ld.gold` or similar
depending on what clang reported.

Gcc will still use -fuse-ld=gold (as it doesn't accept absolute
path argument to `-fuse-ld`).

This is to make the Clang autogenerated toolchain not depend on PATH if
we can help it. Gcc is still leaking the PATH.

The leak:

1) CC is installed in a non-standard location, or is checked-in into the
   workspace.
2) CC is passed to Bazel's cc_configure, Bazel autoconfigures the
   toolchain using CC.
3) Remote worker has CC installed in the same non-standard location, or
   gets CC in action inputs.
4) If Host system has gold on its PATH (potentially to the surprise
   of the user, user might assume that since they provide CC explicitly
   only that installation is used), Bazel will autoconfigure the
   toolchain to use gold linker.
5) Remote system doesn't have gold installed, build fails.

Alternative solutions:
* Pass -B$(dirname $(which gcc)) to CC and pass empty PATH to all
  Bazel's C++ autoconfiguration commands
* Do not detect gold automatically at all, require environment variable
  to be explicitly set to enable gold

Both are backwards incompatible changes. Solution in this PR is
backwards compatible. It's also not fixing the issue for Gcc.

Closes #8580.

PiperOrigin-RevId: 256623542