[clang] [llvm] [TargetVerifier][AMDGPU] Add TargetVerifier. (PR #123609)

[via llvm-commits]

jofrn wrote:

>I don't think it makes sense to have a target-specific "verifier": verification sets the limits of what optimizations are allowed to do. And that determination needs to be target-independent, or else target-independent optimizations can't exist.

This would be run during the backend after we've already selected the target, so it can be target-dependent.

https://github.com/llvm/llvm-project/pull/123609