[libcxx-commits] [libcxx] Refactor dockerfile to support Buildkite AND Github Actions (PR #71954)

[via libcxx-commits]

================
@@ -5,11 +5,29 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 #===----------------------------------------------------------------------===##
-
 #
----------------
EricWF wrote:

I did. I tested (and am using) the `testing` image for the github actions runners, and I ran a few jobs on the buildkite ones (which initially discovered some now addressed issues). 

https://github.com/llvm/llvm-project/pull/71954