[libclc] [libclc] Stop installing CLC headers (PR #126908)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> 
> Maybe there is a better tripple to be used in this case? However we do want to compile to SPIR-V (with the native target in the future anyway), it's just it enables a bunch of things automatically.

I'm not sure I understand what the issue is. The defines here just declare that the extension is available, it does not enable them. You need to use the pragma to actually enable the extension (which the header does to enable required types later on in that file for declarations, but it cleans up after itself with `#pragma OPENCL EXTENSION all : disable` at the end 

https://github.com/llvm/llvm-project/pull/126908