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

[Konrad Kleine via cfe-commits]

kwk wrote:

> > Are you planning to introduce the README.md changes as well? I think it makes sense.
> 
> That's a separate documentation change we should do, right now I'm just waiting for someone to sign off on this so the mesa builds aren't broken

@jhuber6 I've created a small README update here: https://github.com/llvm/llvm-project/pull/196483

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