[libclc] [llvm] [libclc][CMake] Use clang/llvm-ar on Windows (PR #186726)

[Romaric Jodin via cfe-commits]

rjodinchr wrote:

> libclc is an old project, this is trying to 'modernize' it I suppose?

To be clear, I agree that libclc needs to be modernized. The work you have done is great, thank you 🙏. I would not want to go back. I'm just trying to figure out if there is something to fix, or if I need to set up my configuration differently.

https://github.com/llvm/llvm-project/pull/186726