this was likely a typo, we have -Lglib but rpath is for gettext

component/gtk-2/buildout.cfg

@@ -63,7 +63,7 @@ md5sum = 87f20b78deaedef858ac54358c0786b1
 environment = 
   PATH=${glib:location}/bin:${pkgconfig:location}/bin:%(PATH)s
   PKG_CONFIG_PATH=${glib:location}/lib/pkgconfig
-  LDFLAGS=-L${gettext:location}/lib -Wl,-rpath=${gettext:location}/lib -L${glib:location}/lib -Wl,-rpath=${gettext:location}/lib
+  LDFLAGS=-L${gettext:location}/lib -Wl,-rpath=${gettext:location}/lib -L${glib:location}/lib -Wl,-rpath=${glib:location}/lib
   LD_LIBRARY_PATH=${glib:location}/lib:${gettext:location}/lib
 
 [gtk-2]