Overhaul the linker
The linker has gained support for aarch64/macho, and aarch64/elf, as well as improved arm/elf code, this code introduces separate mapping of sections into different pages, to allow for
W^X protection. This is essentially a requirement on iOS, and I believe a sane default to have. To this extend the symbol extras logic needed to be split up into GOT and PLTs, where the PLTs are allocated alongside the sections, as
the architecture may not allow arbitrary jumps (arm/aarch64). The introduction aarch64/elf has also been
done through a pseudo interface so that the actual relocation logic can be contained within it's own files.
Ideally we'd improve the linker by migrating the existing (heavily #ifdef'd) to the new separate section mapping (
W^X) and pseudo interface approach. The separate section mapping logic has an inherent memory inefficiency (which might be improved a bit by aggregating similar sections into the same page), and might also cause a performance penalty due to separate mapping instead of a single file mmap.