[llvm] [libc++][Android] Support libc++ testing on Android (PR #69274)

[via llvm-commits]

https://github.com/EricWF approved this pull request.

This looks good to me. There's a lot of code here, but very little of it modifies anything that is existing.

Let's land this and see how it goes.

https://github.com/llvm/llvm-project/pull/69274