recipe: only allow concurrent extract for tarballs
recipe: only allow concurrent extract for tarballs

Extracting git repos concurrently can result in locking files being hit

nirbheek/cerbero,GStreamer/cerbero,GStreamer/cerbero,nirbheek/cerbero,GStreamer/cerbero,GStreamer/cerbero,nirbheek/cerbero,GStreamer/cerbero,nirbheek/cerbero