[llvm] [llvm-objcopy] Add llvm-objcopy option --set-symbol-visibility (PR #80872)

[James Henderson via llvm-commits]

https://github.com/jh7370 approved this pull request.

Approving, to clear my "changes requested" blocker, but I'd still like to hear from @MaskRay to see if he has any further opinions before this gets merged.

https://github.com/llvm/llvm-project/pull/80872