GTK requires X Windows or DirectFB as a prerequisite. If you have not installed either one, do that first.
Here is a build tree for the AVR32 similar to the tree for X Windows.
* gtk2-avr32.tar.bz2: GTK+ 2 Build tree for AVR32
* gtk-2.10.13-avr32.tar.bz2: GTK+ 2.10.13 binaries for AVR32
The script will install GTK and all of its dependencies to /usr/avr32-linux
* Screenshot of gtk-demo on NGW100: