Here is the patch which I just put in the RHEL5 gtk+ package to fix the gtk-config multilib conflict.
Created attachment 145356 [details] gtk-config patch
Oh, and after the glib multilib fix, gtk+ needs to BR pkgconfig
%changelog * Thu Jan 11 2007 Rex Dieter <rdieter[AT]fedoraproject.org> 1:1.2.10-56 - multilib patch (#222298) - cleanup auto* foo - drop old/deprecated bits
Builds queue'd, thanks.