[lld] [lld-macho] Implement ObjC category merging (-objc_category_merging) (PR #85727)

[via llvm-commits]

alx32 wrote:

Note: This is a re-land of https://github.com/llvm/llvm-project/pull/82928 after fixing using already freed memory in generatedSectionData. This issue was detected by ASAN build.

https://github.com/llvm/llvm-project/pull/85727