[llvm] [AMDGPU][Attributor] Make `AAAMDFlatWorkGroupSize` honor existing attribute (PR #114357)

[John Tramm via llvm-commits]

jtramm wrote:

Ah, it looks like the `.bc` files are binary files. Is there a specific program I need to use to check them for attributes?

https://github.com/llvm/llvm-project/pull/114357