You will have to use 'pkgconfig'.
gtk+-2 has these ".pc" files (also referred to as 'package') :
/usr/lib/pkgconfig/gdk-2.0.pc
/usr/lib/pkgconfig/gdk-x11-2.0.pc
/usr/lib/pkgconfig/gtk+-2.0.pc
/usr/lib/pkgconfig/gtk+-unix-print-2.0.pc
/usr/lib/pkgconfig/gtk+-x11-2.0.pc
I guess, that some pkgconfig recognition is part of autotools.
Some Makefile.in have this line only : PKG_CONFIG = @PKG_CONFIG@
( Please see for yourself in a gtk application or
the gtk+-2 source code itself.)
Examples : Google .. how makefile.in pkgconfig ..
http://www.google.com/webhp#hl=en&q=...ba07cc1e57261b
First hit :
http://www.aleksey.com/xmlsec/api/xm...ling-unix.html
etc. etc.
..
Good luck !