[llvm] Allow specifying libcxx builder image. (PR #110303)

[Michael Buch via llvm-commits]

Michael137 wrote:

> It looks like it's still failing with the latest run :-(

Argh that's unfortunate. How about we skip this test in libc++ CI to unblock this PR. And I'll open a github issue to re-enable the test.

@EricWF It's probably easiest if you just add `--filter-out=TestDAP_subtleFrames.py` to the following LIT invocation as part of this PR: https://github.com/llvm/llvm-project/blob/8c4bc1e75de27adfbaead34b895b0efbaf17bd02/libcxx/utils/ci/run-buildbot#L397

But if you prefer me doing it separately, let me know.

https://github.com/llvm/llvm-project/pull/110303