[libcxx] [llvm] [libc++][WIP] Move to Github hosted builders (PR #109720)

[Tom Stellard via llvm-commits]

https://github.com/tstellar commented:

Would you be able to use ccache or sccache for this job?  It might be necessary to keep the usage down to manageable levels.  See https://github.com/hendrikmuhs/ccache-action.

https://github.com/llvm/llvm-project/pull/109720