ld: warn about PE base relocations to sections above .reloc

ld: warn about PE base relocations to sections above .reloc

Due to a bogus linker script, or perhaps because a section doesn't get
placed by a linker script while default placement puts it too high up,
sections can end up above .reloc. Since the process of determining its
contents (and hence its size) happens before final section placement,
relocations needed for such sections would no longer point at the
correct address in the final binary. Warn about this (down the road this
may want to become an error, unless size determination and content
creation for .reloc would get decoupled).

To avoid triggering the warning when .reloc gets discarded, suppress
populating the section in the first place in this case.