Rather than specifying fragments of sources.list on the command line,
just specify the whole thing. --apt-sources allows you to specify the
/etc/apt/sources.list that will be shipped, and --local-apt-mirror
allows you to specify a local mirror to use (ie, if approx is being
used) when building the chroot.
--distribution, --mirror, and --othermirror have been dropped.
Signed-off-by: Andres Salomon <dilinger@debian.org>