There is no $(use_enable introspection) in the ebuild, making the code look for Gst-0.10.gir, which I don't have since I also do not have gstreamer compiled with USE=introspection. Reproducible: Always
i con confirm this problem too
In future, set the "Component" to "GNOME" so that we get bugs directly. I've fixed this in the overlay, thanks for reporting!