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

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

Why would the output file not be generated correctly? I think at this point it's just a difference in interpretation over what `emitError` should do. It doesn't exit the program, it simply outputs to STDOUT/STDERR that an error occurred, and then the program continues on as normal (with the default eviction advisor in this case).

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