[llvm] [objcopy] Return an error in case of an invalid regex (PR #74319)

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

Nit: the commit/PR title's tag should be llvm-objcopy, not simply  objcopy.

Overall, the patch looks fine. Just a few small comments.

https://github.com/llvm/llvm-project/pull/74319