[lld-macho] Skip over symbols in un-parsed debug info sections

clang appears to emit symbols in `__debug_aranges`, at least
for arm64... in the examples I've seen, it doesn't seem like those
symbols are referenced outside of `__DWARF`, so I think they're safe to
ignore. But hopefully @clayborg can confirm.

Reviewed By: clayborg

Differential Revision: https://reviews.llvm.org/D98073