[libclc] [libclc] use default paths with find_program when possible (PR #105969)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> So it should be built along with the core of LLVM? Also, we package LLVM per version per subproject.

Yes, it should be built along with the core (but doesn't need to ship in the same package as the core). 



https://github.com/llvm/llvm-project/pull/105969