[clang] [llvm] [AMDGPU] Adding the amdgpu-num-work-groups function attribute (PR #75647)

[Krzysztof Drewniak via cfe-commits]

krzysz00 wrote:

I'd go with Matt's point: close this, and then add metadata for required launch grid sizes. Then you can update `AMDGPULowerKernelAttributes` to use said metadata.

https://github.com/llvm/llvm-project/pull/75647