When applying relocations, we need to resolve ABI aliases.
relocsym does that. Architecture-specific archreloc also needs to
do that. The old code doesn't do that since ABI aliases are
resolved in loadlibfull, or, in the old linker, in a much earlier
stage. We don't do this in the new linker, as we want to avoid
mutating relocations.
While here, move R_CONST and R_GOTOFF handling to generic code.
They appear on several architectures and the handling are same.
Should fix 386-clang and *bsd-386 builds.
Change-Id: I6681c94f0327555d6cf329d0a518c88848773671
Reviewed-on: https://go-review.googlesource.com/c/go/+/230857 Reviewed-by: Than McIntosh <thanm@google.com> Reviewed-by: Jeremy Faller <jeremy@golang.org>