cerbero: Don't serialize extract on Windows
cerbero: Don't serialize extract on Windows

tarfile is single-threaded and quite slow.

Part-of: <https://gitlab.freedesktop.org/gstreamer/cerbero/-/merge_requests/616>

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