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

[Joseph Huber via llvm-commits]

jhuber6 wrote:

Yeah, crashing on an unhandled error is definitely incorrect, whether or not it should be ignored is a different issue but I can see the rationale. I think `clang` stops as well if `-fpass-plugin=` doesn't point to a valid library so there's lots of precedent.

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