[clang] [clang] Rename files that MacOS libtool warns about (NFC) (PR #150054)

[Farzon Lotfi via cfe-commits]

farzonl wrote:

This change will absolutely fix the issue, I was advised on my few attempts that we want to be able to keep the same name and the fix should be in cmake and not a file rename.

For example We have many `AMDGPU.cpp`
- clang/lib/Basic/Targets/AMDGPU.cpp
- clang/lib/CodeGen/Targets/AMDGPU.cpp
- clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp

And we want to be able to keep reusing the AMDGPU.cpp name but it requires us to not reuse that name in the same cmake file and to have one cmake file per directory.

https://github.com/llvm/llvm-project/pull/150054