[clang] [llvm] [lld] [flang] [AMDGPU] Introduce GFX9/10.1/10.3/11 Generic Targets (PR #76955)

[Pierre van Houtryve via cfe-commits]

Pierre-vh wrote:

I added a few more tests, I just didn't find how to test the flat-scratch stuff properly.
Also, gfx904 is documented as not having absolute flat scratch, yet I don't see anything about that in the code (no related feature). I put gfx9-generic with flat scratch but I don't know if that's correct at all, and how to test it?

https://github.com/llvm/llvm-project/pull/76955