[libcxx-commits] [libcxx] [libcxx] Install runner last when building CI containers (PR #148072)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne commented:

Does `./libcxx/utils/ci/run-buildbot-container` still work after this change? LGTM assuming it does.

Also, we'll need to test this change before we switch to this image: that can be done by building this image, associating it to the `-next` GH runner group inside llvm-zorg, and then creating a PR that changes our workflows to target the `-next` runners. Kinda complicated, but that's the simplest we have until we can specify an image directly inside the GH workflow file.

https://github.com/llvm/llvm-project/pull/148072