This makes two basic changes, 1 it moves the name of the linker into the
linker class, this should reduce the number of errors and typos, and
ensure that a linker always has one name. This then renames the linkers
to have more consistent names.
Posix/gnu linkers are called ld.<name>: ld.gold, ld.lld, ld.solaris.
Apple linkers are renamed ld64.