Building gcc with gnu binutils automatically

[NightStrike]

If you use gnu ld or as to build GCC, you get extra features in gcc
itself.  There's a few bugzilla PRs on this, and a lot of emails on
the mailing list.  What I don't see, however, is how I can have
configure detect the usage of GNU binutils automatically.  In other
words, without explicitly passing in --with-gnu-ld/as, I don't get the
features in question.

Is there a way to do this?  Or, is there a way to fix configure so
that it does some test without requiring the option?  Also, is there a
way to do this for a cross compiler?