[llvm] [LTO] Avoid assert fail on failed pass plugin load (PR #96691)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 approved this pull request.

Good catch, we definitely need to consume the error in the failure state for proper behavior.

I wonder if we could make a lint for this in the LLVM codebase.

https://github.com/llvm/llvm-project/pull/96691