[MachO][ObjCopy] Handle exports trie in LC_DYLD_INFO and LC_DYLD_EXPORTS_TRIE

The exports trie used to be pointed by the information in LC_DYLD_INFO,
but when chained fixups are present, the exports trie is pointed by
LC_DYLD_EXPORTS_TRIE instead.

Modify ObjCopy code to calculate the right offset and size needed
depending on the existence of LC_DYLD_INFO or LC_DYLD_EXPORTS_TRIE, read
the exports from either of those places, and write the export
information as pointed to either of those places.

Depends on D134571.

Reviewed By: alexander-shaposhnikov

Differential Revision: https://reviews.llvm.org/D137879