I thought this would allow insertion with ld.gold, but it turns out
that the resulting binary has something wrong with sections. So only the
change to the script is committed, because it makes it much easier to
experiment with various linkers.
READONLY is supported in ld.bfd from binutils >= 2.38, though the
patch was backported in rawhide. It is also unsupported by ld.gold,
so let's make it easy to skip it, since things will also work without
it, just a tiny bit worse.
