[libclc] [libclc] Only check the triple architecture for libclc (PR #194149)

[Michał Górny via cfe-commits]

mgorny wrote:

So there is no reason to build three different nvidia triples that were on the list before?

```
nvptx64--
nvptx64--nvidiacl
nvptx64-nvidia-cuda
```

https://github.com/llvm/llvm-project/pull/194149