This only fixes it when using object::write as backend, and not when using faerie.
There were two problems:
* object::write doesn't replace .debug_info with __debug_info, unlike faerie
* machO requires section relative relocations, and not symbol relative
relocations. When using symbol relative relocations, the linker
interprets the relocations as section relative. Thus writing the wrong
values to the debug sections.
Fixes#303
