ibus-engines.libpinyin: Fix typelib finding

Same as 9f7bd20a99.

Fixes `ValueError: Namespace Gtk not available for version 3.0` when
opening ibus-setup-libpinyin from gnome-control-center (when `cat
./result/libexec/ibus-setup-libpinyin` you will now find GI_TYPELIB_PATH
being passed to makeCWrapper).

The issue can be not reproducible on some impure environments,
I guess the best way to test is to directly run
GI_TYPELIB_PATH= ./result/libexec/ibus-setup-libpinyin

pkgs/tools/inputmethods/ibus-engines/ibus-libpinyin/default.nix

@@ -4,6 +4,7 @@
   fetchFromGitHub,
   autoreconfHook,
   gettext,
+  gobject-introspection,
   pkg-config,
   wrapGAppsHook3,
   sqlite,
@@ -34,6 +35,7 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [
     autoreconfHook
     gettext
+    gobject-introspection.setupHook
     pkg-config
     wrapGAppsHook3
   ];