libgtop: add dev output

This will prevent glib.dev from propagatedBuildInputs from ending in the out closure.

pkgs/development/libraries/libgtop/default.nix

@@ -13,6 +13,8 @@ stdenv.mkDerivation rec {
   pname = "libgtop";
   version = "2.40.0";
 
+  outputs = [ "out" "dev" ];
+
   src = fetchurl {
     url = "mirror://gnome/sources/${pname}/${lib.versions.majorMinor version}/${pname}-${version}.tar.xz";
     sha256 = "1m6jbqk8maa52gxrf223442fr5bvvxgb7ham6v039i3r1i62gwvq";