Add a Python 3.x sub-port of py-libarchive-c, in order for a port of the
Debian diffoscope project to be created, which is Python 3 only. This
(py3-*) hack^W workaround ensures a py3x-* package can be created by
default.
- Allow USES to be overriden in base port accordingly
While I'm here
- Enable NO_ARCH
Requested by: emaste, bapt (for diffoscope, reproducible builds)
