drc: make sure dyna_linker is really called from stub

drc: make sure dyna_linker is really called from stub

in very rare cases add_link() would end up being called with jump to
another block and not stub, which would later cause kill_pointer() to
crash while cleaning jump_out. I'm guessing wrong pointer was being
picked from jump_in by dyna_linker, failing to detect stale cache,
and hoping this will fix it.