[llvm] RegAlloc: Fix verifier error after failed allocation (PR #119690)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> @arsenm any luck with the CodeGen/AMDGPU/register-killed-error-after-alloc-failure0.mir test failure?

I get different stack IDs for the spills on macOS. Not sure how much I should care, I could just hack around it with a regex check line 

https://github.com/llvm/llvm-project/pull/119690