[libclc] [libclc] Add initial support for libclc execution conformance tests (PR #214072)

[Wenju He via cfe-commits]

wenju-he wrote:

> I think there's been attempts by some people at Intel to get the LevelZero infrastructure working through the `llvm-gpu-loader` tool. I don't know what status it's in currently, however. I'd assume it would need to be the `spirv64-intel` triple

Attempt in offload directory? spir64/spirv64 (not fully transitioned to spirv64 yet) is still the triple that Intel supports in current products.
There will be a new pisa triple that will be upstreamed, and then there will be corresponding support will be upstreamed to offload directory.

https://github.com/llvm/llvm-project/pull/214072