[libcxx] [llvm] [libc++] Move some macOS CI jobs to Github actions (PR #89083)

[Louis Dionne via llvm-commits]

ldionne wrote:

> > Yes, we could do that or we could pay for additional capacity on Github directly. I have been maintaining the Foundation macOS nodes and not having to do that anymore is the main motivation for this change.
> 
> Would we be able to repurpose those machines into self-hosted GitHub runners? If so, I can help with the maintenance of those machines. That would help ensure we have the capacity we need.

Yes, that should be possible. I will start by making it work for the Github-provided builders and then we can tackle the capacity increase as a separate task.

https://github.com/llvm/llvm-project/pull/89083