[llvm] [CI] Run Linux premerge CI on libc++ changes. (PR #155188)

[Michael Buch via llvm-commits]

Michael137 wrote:

Oh I see @philnik777 already chimed in.

I think i see what happened.

The test that failed was skipped on Linux for the longest time. I re-enabled it very recently specifically to catch libc++<->LLDB breakages: https://github.com/llvm/llvm-project/pull/157649

But the pre-merge CI on the libc++ PR probably ran without being rebased on that change. So the test was skipped.

I think at this point all the libc++-specific tests in LLDB are run as part of the bootstrapping build

https://github.com/llvm/llvm-project/pull/155188