[libclc] [libclc] Fix using normalized triple for the directory name (PR #194607)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> `clspv` doesn't actually utilize the `clspv--` or `clspv64--` triples; since it simply consumes the generated binaries, those names are arbitrary and can easily be updated.
> 
> **The primary requirement is keeping a method to target the specific `clspv` path within `libclc`.** 
> Once inside the `clspv` workflow, the system actually relies on `spir-unknown-unknown` and `spir64-unknown-unknown` triples. While some cleanup might be necessary, that remains an internal task for the `clspv` side.
> 
> cc @alanbaker @dneto for visibility.

What we should do is make the canonical triple for your target `spirv64-unknown-vulkan` and then change clang to add a `__VULKAN__` macro like how people already handle `__WIN32` or `__LINUX__`. I'll look into that

https://github.com/llvm/llvm-project/pull/194607