build: make autobuild require rpm build deps

build: make autobuild require rpm build deps

I spent far too long on a new machine trying to figure out why
./autobuild.sh failed due to an rpm build failure (complaining
that libvirt_parthelper was supposed to be packaged but was not
built), and finally traced it to a missing parted-devel
installation.  I learned that --nodeps is in place for
autobuilder setups, but for developers, removing it would make
rpmbuild error out much sooner for a less cryptic failure.

* autobuild.sh: Conditionally drop --nodeps from rpmbuild lines.

Signed-off-by: Eric Blake <eblake@redhat.com>