[libclc] [libclc][CMake] Use per-source include flags instead of target-level includes (PR #185598)

[Matt Arsenault via cfe-commits]

https://github.com/arsenm commented:

I think this collides with or is redundant with a change I'm looking at making. I don't like this weird system where it's performing source level overrides of functions. I want to move this to a system where there are one or more distinct library builds per target, and linked normally. The function overriding can be performed at a symbol level, rather than file, by the linker 

https://github.com/llvm/llvm-project/pull/185598