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

[Pierre van Houtryve via cfe-commits]

https://github.com/Pierre-vh commented:

Missing components:

- Need a way for external tools to inquire about the specifics of generic targets  (without depending on llvm)
  - map a specific gfx target to its generic family
  - given a specific gfx version, what's the minimum generic version it needs (?)
  - tools need to tell generic MACHs from specific ones (currently they can do that by just doing EFLAGS >> 24 and checking if there is any value other than 0 there, but it needs to be documented)

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