[llvm] [AMDGPU] Fix crash when a MachineFunction is not generated (PR #87727)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

This is a hack that doesn't fully address the underlying issue. You can manifest the same assertion with a function that still needs to be emitted, but also isn't visible in the calligraph (e.g. an @llvm.used function with no callers). @JanekvO was working on moving the resource computation into MC to avoid this issue 

https://github.com/llvm/llvm-project/pull/87727