//PKG_CONFIG_PATH
/sw/lib/pkgconfig:/usr/X11R6/lib/pkgconfig:/Library/Frameworks/Mono.framework/Versions/Current/lib/pkgconfig/

//ERROR 
checking for pkg-config... /sw/bin/pkg-config
checking for gtk+-2.0 >= 2.3.0
        libxml-2.0 >= 2.5.0
        libgnomeprint-2.2 >= 2.2.0... Package gtk+-2.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `gtk+-2.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'gtk+-2.0' found

configure: error: Library requirements (gtk+-2.0 >= 2.3.0
        libxml-2.0 >= 2.5.0
        libgnomeprint-2.2 >= 2.2.0) not met; consider adjusting the PKG_CONFIG_PATH environment variable if your libraries are in a nonstandard prefix so pkg-config can find them.