With glibc upgraded, media-plugins/gst-plugins-v4l2 fails to build.

The specific failure is this:

/var/tmp/portage/media-plugins/gst-plugins-v4l2-1.14.4/work/gst-plugins-good-1.14.4/sys/v4l2/ext/types-compat.h:44:15: error: conflicting types for ‘guint64’ 

The bug is documented, and a fix applied, here: https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/issues/635

Regarding how to fix this, I have taken a look at the gstreamer eclass, and it could easily be replaced with an autogen.yaml and a generator. I suggest we take this approach for updating the entire gstreamer suite. gst-plugins-good contains a lot of the plugins and they all have separate ebuilds. We could potentially have stub ebuilds generated for each of the plugins and just a central parent ebuild that installs stuff.