Fix link error when newer versions of required libs are installed locally

Fixes order of directories specified by -L's so the ones containing newer
glib/gtk will be searched before directories with the older libraries.

plug-ins/file-ico/Makefile.am

@@ -48,8 +48,8 @@ LDADD = \
 	$(libgimpcolor)		\
 	$(libgimpmath)		\
 	$(libgimpbase)		\
+	$(GTK_LIBS)             \
 	$(PNG_LIBS)		\
-	$(GTK_LIBS)		\
 	$(RT_LIBS)		\
 	$(INTLLIBS)		\
 	$(file_ico_RC)