Add gobjectIntrospection to the scope

pkgs/development/libraries/libgtop/default.nix

···
-{ stdenv, fetchurl, glib, pkgconfig, perl, intltool }:
+{ stdenv, fetchurl, glib, pkgconfig, perl, intltool, gobjectIntrospection }:
 stdenv.mkDerivation {
   name = "libgtop-2.32.0";