This target grabs the latest Travis containers from their repository at
quay.io and then installs QEMU's build dependencies. With this it is
possible to run on broadly the same setup as they have on travis-ci.org.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20161011161625.9070-2-alex.bennee@linaro.org>
Signed-off-by: Fam Zheng <famz@redhat.com>