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

[Fangrui Song via llvm-commits]

MaskRay wrote:

> > I think GNU objcopy is likely willing to accept `--set-symbol-visibility`.`--set-symbols-visibility filename=visibility` seems to match the convention that uses `filename` for an option named `*symbols*`, but the infix instead of suffix use of `symbols` is a new convention. I do like `--set-symbols-visibility` and cannot find a better alternative, though.
> 
> So as I understood, please correct me if I'm wrong, that for now we leave the option names and format as is.

Yes. The option names are good as is.

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