Handle the case where there are both common and non-common definitions
of the same symbol. Add a bunch of tests to ensure compatibility with ld64.
Reviewed By: #lld-macho, gkm
Differential Revision: https://reviews.llvm.org/D86910
These opcodes tell dyld to coalesce the overridden weak dysyms to this
particular symbol definition.
Reviewed By: #lld-macho, smeenai
Differential Revision: https://reviews.llvm.org/D86575