gconf: Use a dev output

This reduces the closure size of gconf from 225 to 63 MiB.

+2
+2
pkgs/desktops/gnome-3/3.22/core/gconf/default.nix
··· 24 25 # ToDo: ldap reported as not found but afterwards reported as supported 26 27 meta = with stdenv.lib; { 28 homepage = http://projects.gnome.org/gconf/; 29 description = "A system for storing application preferences";
··· 24 25 # ToDo: ldap reported as not found but afterwards reported as supported 26 27 + outputs = [ "out" "dev" ]; 28 + 29 meta = with stdenv.lib; { 30 homepage = http://projects.gnome.org/gconf/; 31 description = "A system for storing application preferences";