fix(ci): Use pre-built docker images

In this change we modify the CI pipeline to use pre-built Docker images
for both build and deploy stages.  To this end, we create
`docker/{build-env,deploy-env}`, two directories containing Dockerfiles
describing how to build those images, and scripts to push them to a
Docker registry.

Currently, docker.card10.badge.events.ccc.de seems broken. Thus, we push
to the Warsaw Hackerspace Docker registry.  Since the Docker images will
be pulled rarely anyway (as they are cached by build nodes), any low
bandwidth-caused slowdowns will not be usually end up in the CI critical
path.

We also bump `.gitlab-ci.yml` to point to those new images.

.gitlab-ci.yml

-image: "debian"
+# maintained by q3k, built using docker/build-env
+image: "registry.k0.hswaw.net/q3k/card10-build-env:20190725-110707Z-4f3bf2a"
 
 build:
     stage: build
-    before_script:
-        - echo "deb http://deb.debian.org/debian stretch-backports main" >> /etc/apt/sources.list
-        - apt update -qq
-        - apt install -y -qq gcc-arm-none-eabi python3-pip git
-        - apt install -y -qq -t stretch-backports meson
-        - pip3 install crc16
     script:
         - ./bootstrap.sh
         - ninja -C build/
@@ -15,11 +10,8 @@ build:
 
 pages:
     stage: deploy
-    image: ubuntu:bionic
-    before_script:
-        - apt update -qq
-        - apt install -y -qq python3-pip git clang libclang-dev llvm
-        - pip3 install sphinx sphinx_rtd_theme clang
+    # maintaned by q3k, build using docker/deploy-env
+    image: "registry.k0.hswaw.net/q3k/card10-deploy-env:20190725-112709Z-4c5d8e8"
     script:
         - export LD_LIBRARY_PATH=$(llvm-config --libdir)
         - echo $LD_LIBRARY_PATH

docker/build-env/Dockerfile

+FROM debian:stretch-backports
+
+RUN set -e -x ;\
+    export DEBIAN_FRONTEND=noninteractive ;\
+    apt-get update -y ;\
+    apt-get install -y \
+        git \
+        gcc-arm-none-eabi \
+        python3-pip ;\
+    apt-get install -y -t stretch-backports \
+        meson ;\
+    pip3 install crc16 ;\
+    rm -rf /var/lib/apt/lists
+

docker/build-env/push.sh

+#!/usr/bin/env bash
+
+# Build and push the build env Docker container to the Gitlab container registry.
+
+set -e
+
+function rev() {
+    ( cd $1; git describe --always --match "v[0-9].*" --dirty )
+}
+
+IMAGE=registry.k0.hswaw.net/q3k/card10-build-env
+TAG=$(TZ=UTC date +%Y%m%d-%H%M%SZ)-$(rev .)
+
+docker build -t $IMAGE:$TAG .
+docker push $IMAGE:$TAG
+
+echo "Pushed $IMAGE:$TAG"

docker/deploy-env/Dockerfile

+FROM ubuntu:bionic
+
+RUN set -e -x ;\
+    export DEBIAN_FRONTEND=noninteractive ;\
+    apt-get update -y ;\
+    apt-get install -y \
+        clang \
+        git \
+        libclang-dev \
+        llvm \
+        python3-pip ;\
+    pip3 install \
+        clang \
+        sphinx \
+        sphinx_rtd_theme ;\
+    rm -rf /var/lib/apt/lists
+

docker/deploy-env/push.sh

+#!/usr/bin/env bash
+
+# Build and push the deploy env Docker container to the Gitlab container registry.
+
+set -e
+
+function rev() {
+    ( cd $1; git describe --always --match "v[0-9].*" --dirty )
+}
+
+IMAGE=registry.k0.hswaw.net/q3k/card10-deploy-env
+TAG=$(TZ=UTC date +%Y%m%d-%H%M%SZ)-$(rev .)
+
+docker build -t $IMAGE:$TAG .
+docker push $IMAGE:$TAG
+
+echo "Pushed $IMAGE:$TAG"