[libclc] [libclc] Set OpenCL C version for each target (PR #135733)

[Wenju He via cfe-commits]

wenju-he wrote:

> Targets may even want to compile libclc for multiple different versions? That might introduce extra complexity (we'd need "an extra loop", more compilation time, new naming/versioning schemes for the build artifacts).

An application may compile using different -cl-std version, but IIUC such usage is incompatible with a target which supports a specific OpenCL version. So compiling for the target's supported OpenCL version might be enough.

https://github.com/llvm/llvm-project/pull/135733