[libcxx] CI: set symbolizer for bootstrapping build

[mizvekov]

Summary

Setting the symbolizer is required for getting a pretty
stack trace when Clang crashes.

Signed-off-by: Matheus Izvekov <[e-mail]>

[ldionne]

libcxx/utils/ci/run-buildbot

474 ↗

(On Diff #456184)

What tool picks up that environment variable? With a quick search, it looks like clang itself looks for it and symbolizes the crash trace when it can find it.

We are trying to keep run-buildbot agnostic of the versions of tools available on the CI machine, so this may belong more in` buildkite-pipeline.yml`, or perhaps we should also simply make llvm-symbolizer available in the $PATH on our CI nodes by changing libcxx/utils/ci/Dockerfile.

[mizvekov]

libcxx/utils/ci/run-buildbot

474 ↗

(On Diff #456184)

Yeah that is the case, we need that so that we can have readable crash traces in the CI output.

Setting that variable for all configurations, or just making the unversioned tool available, would also help with crash traces in configurations other than the bootstrapping-build, so I will follow one of those approaches.

[Mordante]

I love the idea of this change, but I too like it to use a different approach.

libcxx/utils/ci/run-buildbot

474 ↗

(On Diff #456184)

I prefer the utils/ci/buildkite-pipeline.yml approach since we try to keep both
this file and the Dockerfile version agnostic

Can you add LLVM_SYMBOLIZER_PATH to utils/ci/buildkite-pipeline.yml like:
(Note these changes are very recent so you might need to rebase.)

- label: "Bootstrapping build"
  command: "libcxx/utils/ci/run-buildbot bootstrapping-build"
  artifact_paths:
    - "**/test-results.xml"
    - "**/*.abilist"
  env:
      CC: "clang-${LLVM_HEAD_VERSION}"
      CXX: "clang++-${LLVM_HEAD_VERSION}"
      LLVM_SYMBOLIZER_PATH: "/usr/bin/llvm-symbolizer-${LLVM_HEAD_VERSION}"
  agents:
    queue: "libcxx-builders"
    os: "linux"
  retry:
    automatic:
      - exit_status: -1  # Agent was lost
        limit: 2
  timeout_in_minutes: 120

[mizvekov]

In D132807#3755672, @Mordante wrote:

I love the idea of this change, but I too like it to use a different approach.

Done, thanks!

[Mordante]

LGTM! Thanks! I leave the final approval to @ldionne.

libcxx/utils/ci/buildkite-pipeline.yml

steps:
   - label: "Bootstrapping build"
     command: "libcxx/utils/ci/run-buildbot bootstrapping-build"
     artifact_paths:
       - "**/test-results.xml"
       - "**/*.abilist"
     env:
         CC: "clang-${LLVM_HEAD_VERSION}"
         CXX: "clang++-${LLVM_HEAD_VERSION}"
+        LLVM_SYMBOLIZER_PATH: "/usr/bin/llvm-symbolizer-${LLVM_HEAD_VERSION}"
     agents:
       queue: "libcxx-builders"
       os: "linux"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
     timeout_in_minutes: 120