[llvm-objcopy][MachO] Support indirect symbol table
Summary:
Parse the indirect symbol table and update the indexes of
symbol entries in the table in the writer in case they have
been changed.
Reviewers: alexshap, rupprecht, jhenderson
Reviewed By: alexshap, rupprecht
Subscribers: jakehehrlich, abrachet, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D66280