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

[Richard Dzenis via llvm-commits]

RIscRIpt wrote:

Thank you for reviews! I took another look at my tests and realized that I can remove `LC_DYSYMTAB` load command - that's what I did in the another fixup commit.

I'll merge this PR once all pre-merge checks pass.

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