That doesn't help during the ./configure run. Bruno Haible (gettext maintainer) has a solution for what you want: http://mail.gnu.org/archive/html/autoconf/2002-05/msg00124.html
Wow, I never saw that before, that would be very nice. I too have struggled with trying to use libtool at configure-time to check libraries and things for use by the application, and I'd like to see some Autoconf help in that area.
