[clang] [Clang][OpenCL][AMDGPU] OpenCL Kernel stubs should be assigned alwaysinline attribute (PR #137769)

[Yaxun Liu via cfe-commits]

yxsamliu wrote:

> > In practice this should be a single use of an internal function and should not require this hint. Is this papering over a different issue?
> 
> Why do you think it is an internal function? I thought it's an externally callable stub.

Agree. OpenCL allows calling an external kernel function https://godbolt.org/z/ThPKfxKqo so the stub function should have external linkage.

https://github.com/llvm/llvm-project/pull/137769