More speed increases for make-ing ports

[Stephen Montgomery-Smith]

This small modification cuts off about 25% off pkg_version on my system.

Basically bsd.gnome.mk recursively finds all the dependencies, but many 
of them are listed many times.  This makes make work extra hard when it 
doesn't have to.  I simply weed out the repeated entries.

-------------- next part --------------
--- bsd.gnome.mk-orig	Tue May 22 01:29:08 2007
+++ bsd.gnome.mk	Tue May 22 01:29:22 2007
@@ -655,6 +655,8 @@
 _USE_GNOME+=	${${component}_USE_GNOME_IMPL} ${component}
 . endfor
 
+_USE_GNOME!=(for i in ${_USE_GNOME}; do ${ECHO_CMD} $$i; done) | sort -u
+
 # Setup the GTK+ API version for pixbuf loaders, input method modules,
 # and theme engines.
 PLIST_SUB+=			GTK2_VERSION="${GTK2_VERSION}"