tests/docker/dockerfiles: new debian-bootstrap.docker

tests/docker/dockerfiles: new debian-bootstrap.docker

Together with the debian-bootstrap.pre script can now build an arbitrary
architecture of Debian using debootstrap. This allows debootstrap to set
up its first stage before the container is built.

To build a container you need a command line like:

  DEB_ARCH=armhf DEB_TYPE=testing \
    ./tests/docker/docker.py build \
    --include-executable=arm-linux-user/qemu-arm debian:armhf \
    ./tests/docker/dockerfiles/debian-bootstrap.docker

Although a number of non-debian systems package the debootstrap script
it is fairly portable in itself. Assuming we have some sort of fakeroot
implementation we can just clone the upstream repository and use the
script from there.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1468934445-32183-5-git-send-email-famz@redhat.com
Signed-off-by: Fam Zheng <famz@redhat.com>