[llvm] [llvm-objcopy] Add support of symbol modification flags for MachO (PR #120895)

[Richard Dzenis via llvm-commits]

RIscRIpt wrote:

I was not sure if I have to adjust `N_PEXT` flag in case we are applying either "localization" or "globalization". So I just keep it unchanged. Please let me know if this is not correct.

https://github.com/llvm/llvm-project/pull/120895