1. If an object file was not compiled with `MH_SUBSECTIONS_VIA_SYMBOLS`
   such a hand-written ASM on x86_64, treat the entire object file as
   not suitable for dead code stripping aka a GC root.
2. If there are non-extern relocs within a section, treat the entire
   section as a root, at least temporarily until we work out the exact
   conditions for marking the atoms live.