[llvm] Fix error message when regalloc eviction advisor analysis could not be created (PR #72165)

[via llvm-commits]

pcc wrote:

I think you're referring to an atypical case where a program prints an error and continues anyway. By default I would expect programs to fail if they encounter an error, and it's confusing to have the error message assume otherwise. It's fine if the error message doesn't say exactly what happened if the user passed some "ignore all errors" flag.

https://github.com/llvm/llvm-project/pull/72165