[clang] [clang] Allow overriding any global variable address space (PR #195612)

[Pierre van Houtryve via cfe-commits]

Pierre-vh wrote:

After digging into it a bit more, I think I understand what you mean. If I define a `hip_barrier` type, I can set it as the AS of the named barrier type in the ASTContext directly, and it should "just work", or at least work much more smoothly. I'll look into it more and try to get a patch up, thanks

https://github.com/llvm/llvm-project/pull/195612