You need to add gobject-introspection to nativeBuildInputs. The
package contains a setup hook that will collect paths to typelibs and
pass them inside GI_TYPELIB_PATH to the wrapper. See also the
introspection typelibs
section
of the Nixpkgs manual.
Also gtk3-x11 already contains gtk3 so you only want to provide one
of them (and on Linux, they are the same derivation).