[clang] clang: Add builtin header for amdhsa abi (PR #181993)

[Joseph Huber via cfe-commits]

https://github.com/jhuber6 commented:

It's nice to finally have a struct definition of this in tree, I am wondering if this is the right place though. The only user I know of is `offload/` which won't be able to switch to this because it is expected to compile w/ GCC as well. 

https://github.com/llvm/llvm-project/pull/181993