flatdeb-builder: Add new builder

This allows to use flatdeb to build Mildenhall runtime and SDK, using kvm or UML runners.

ARG RELEASE should be declared a second time after FROM to be accessible by RUN commands, cf. https://ryandaniels.ca/blog/docker-dockerfile-arg-from-arg-trouble/

Signed-off-by: Frédéric Danis frederic.danis@collabora.com

apertis-flatdeb-builder/bin/debos-wrapper

+#!/bin/sh
+
+set -e
+
+if [ -f /tmp/libslirp ]; then
+    rm /tmp/libslirp
+fi
+
+slirp-seq --listen-seqsocket-path=/tmp/libslirp \
+          --exit-with-parent &
+
+
+exec debos.real "$@"