Fix issue where generated RPMs had root:root perms

This resolves an issue which was causing the actual RPMs
generated by Delorean on the host machine to be owned
by root:root. This is due to the fact that we use root
within the container to generate the RPMs which are
then copied into the data directory.

This approach passes the UID/GUID of the process calling
delorean into the script which then uses that information
to chown the resulting data files once the build finishes.

This change also updates the ~/rpmbuild/ paths to be based
on the user ~ homedir instead of just /rpmbuild (this
fixed builds for me).