[clang] [llvm] [NVPTX] Support __usAtomicCAS builtin (PR #99646)

[via cfe-commits]

DenisGZM wrote:

> Have sent you a PR to your branch with one test file :) Hope that helps!

Thanks a lot! Still need some time to get used to these unit tests, but it's getting better :)

https://github.com/llvm/llvm-project/pull/99646