According to our support policy, Debian 9 is not supported by the
QEMU project anymore. Since we now switched the MinGW cross-compiler
builds to Fedora, we do not need these Debian9-based containers
in the gitlab-CI anymore, and can now also get rid of the "layer3"
container build stage this way.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200921174320.46062-3-thuth@redhat.com>
Message-Id: <20200925154027.12672-11-alex.bennee@linaro.org>