Debian packaging via dh_virtualenv (#4285)

docker/Dockerfile-dhvirtualenv

@@ -0,0 +1,35 @@
+# A dockerfile which builds a docker image for building a debian package for
+# synapse. The distro to build for is passed as a docker build var.
+#
+# The default entrypoint expects the synapse source to be mounted as a
+# (read-only) volume at /synapse/source, and an output directory at /debs.
+#
+# A pair of environment variables (TARGET_USERID and TARGET_GROUPID) can be
+# passed to the docker container; if these are set, the build script will chown
+# the build products accordingly, to avoid ending up with things owned by root
+# in the host filesystem.
+
+# Get the distro we want to pull from as a dynamic build variable
+ARG distro=""
+FROM ${distro}
+
+# Install the build dependencies
+RUN apt-get update -qq -o Acquire::Languages=none \
+    && env DEBIAN_FRONTEND=noninteractive apt-get install \
+        -yqq --no-install-recommends -o Dpkg::Options::=--force-unsafe-io \
+        build-essential \
+        debhelper \
+        devscripts \
+        dh-systemd \
+        dh-virtualenv \
+        equivs \
+        lsb-release \
+        python3-dev \
+        python3-pip \
+        python3-setuptools \
+        python3-venv \
+        sqlite3 \
+        wget
+
+WORKDIR /synapse/source
+ENTRYPOINT ["bash","/synapse/source/docker/build_debian.sh"]