[llvm] [CMake] Enable CMP0156 if available (PR #115046)

[Saleem Abdulrasool via llvm-commits]

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

Smaller command lines are also easier to diagnose, and so this should help more generically on non-ELF targets really.

https://github.com/llvm/llvm-project/pull/115046