A Tale of Two PKGBUILDS
Actually four, two for each gstreamer component.
The x86_64 and i686 packages build from the same source, but they
will not build from the same source tree! Build one, then the other
in whatever order you like. Luckily, makepkg takes care of remaking
the source tree prior to each build.

Also in this commit: ported the common-submodule.patch to gst-
plugins-base-git-multilib. Letting makepkg take care of this
download saves a little time and bandwidth on each rebuild.