[llvm] [Offload] Ensure all `llvm::Error`s are handled (PR #137339)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 commented:

These definitely slip by, thanks for addressing it. Think we could have a utility function that converts an LLVM error into one of the offload ones? In the future ideally we will emit the LLVM errors with the appropriate codes and we can just forward the contained code.

https://github.com/llvm/llvm-project/pull/137339