cross compile docker images with docker buildx

.gitlab-ci.yml

@@ -1,11 +1,12 @@
 variables:
   DOCKER_TLS_CERTDIR: "/certs"
+  DOCKER_DRIVER: overlay2
 
 services:
-  - docker:20.10.0-dind
+  - docker:dind
 
 .build: &build
-  image: docker:20.10.0
+  image: docker:latest
   stage: build
   script:
     - docker login -u gitlab-ci-token -p "${CI_JOB_TOKEN}" "${CI_REGISTRY}"
@@ -15,6 +16,25 @@ services:
     - docker push "${CI_REGISTRY_IMAGE}/${NAME}:${CI_COMMIT_REF_SLUG}"
     - if [[ "${CI_COMMIT_REF_SLUG}" == "main" ]]; then docker tag "${CI_REGISTRY_IMAGE}/${NAME}:${CI_COMMIT_REF_SLUG}" "${CI_REGISTRY_IMAGE}/${NAME}:latest" && docker push "${CI_REGISTRY_IMAGE}/${NAME}:latest"; fi
 
+.docker-multiarch-image: &docker-multiarch-image
+  image: jdrouet/docker-with-buildx:stable
+  stage: build
+  tags: [docker-builder]
+  before_script: # per recommendations from https://github.com/docker/buildx/issues/495#issuecomment-754200673
+    - docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
+    - docker buildx create --name cibuilder --driver docker-container --use
+    - docker buildx inspect --bootstrap
+    - docker login -u gitlab-ci-token -p "${CI_JOB_TOKEN}" "${CI_REGISTRY}"
+  script:
+    - docker buildx build --platform "${PLATFORM}" -f "${DOCKERFILE}" -t "${CI_REGISTRY_IMAGE}/${NAME}:${CI_COMMIT_SHA:0:8}" -t "${CI_REGISTRY_IMAGE}/${NAME}:${CI_COMMIT_REF_SLUG}" --push .
+    - if [[ "${CI_COMMIT_REF_SLUG}" == "main" ]]; then docker buildx build --platform "${PLATFORM}" -f "${DOCKERFILE}" -t "${CI_REGISTRY_IMAGE}/${NAME}:latest" --push . ; fi
+  parallel:
+    matrix:
+      - PLATFORM:
+        - linux/amd64
+        - linux/arm64/v8
+        - linux/arm/v7
+
 signal-server:
   image: docker:20.10.0
   stage: build
@@ -52,22 +72,20 @@ test-helper:
     NAME: "test-helper"
   allow_failure: true
 
-builder-image:x86:
+signal-cross-builder:
   <<: *build
   variables:
-    DOCKERFILE: "signald-builder.Dockerfile"
+    DOCKERFILE: "signald-cross-builder.Dockerfile"
-    NAME: "signald-builder-x86"
+    NAME: "signald-cross-builder"
 
-builder-image:aarch64:
+builder-image-alpine:
-  <<: *build
+  <<: *docker-multiarch-image
-  tags: [arm-docker-builder]
-  variables:
-    DOCKERFILE: "signald-builder.Dockerfile"
-    NAME: "signald-builder-arm"
-
-builder-image-alpine:aarch64:
-  <<: *build
-  tags: [arm-docker-builder]
   variables:
     DOCKERFILE: "signald-builder-alpine.Dockerfile"
     NAME: "signald-builder-alpine-arm"
+
+signald-builder:
+  <<: *docker-multiarch-image
+  variables:
+    DOCKERFILE: "signald-builder.Dockerfile"
+    NAME: "signald-builder"

signald-builder.Dockerfile

@@ -1,6 +1,6 @@
 FROM debian:latest
-RUN dpkg --add-architecture armhf && dpkg --add-architecture arm64
 ADD apt-signing-key.asc /tmp/apt-signing-key.asc
+RUN for p in dpkg-split dpkg-deb tar rm; do ln -s /usr/bin/$p /usr/sbin/$p; done
 RUN apt-get update && apt-get install -y \
   gpg \
   dpkg-dev \
@@ -16,8 +16,6 @@ RUN apt-get update && apt-get install -y \
   jq \
   aptly \
   build-essential \
-  crossbuild-essential-armhf \
-  crossbuild-essential-arm64 \
   && rm -rf /var/lib/apt/lists/*
 
 COPY deb-scripts/release-deb.sh /usr/bin/release-deb

signald-cross-builder.Dockerfile

@@ -0,0 +1,29 @@
+FROM debian:latest
+RUN dpkg --add-architecture armhf && dpkg --add-architecture arm64
+ADD apt-signing-key.asc /tmp/apt-signing-key.asc
+RUN apt-get update && apt-get install -y \
+  gpg \
+  dpkg-dev \
+  apt-utils \
+  wget \
+  dh-make \
+  debhelper \
+  javahelper \
+  gradle \
+  default-jdk-headless \
+  git-buildpackage \
+  gradle-debian-helper \
+  jq \
+  aptly \
+  build-essential \
+  crossbuild-essential-armhf \
+  crossbuild-essential-arm64 \
+  && rm -rf /var/lib/apt/lists/*
+
+COPY deb-scripts/release-deb.sh /usr/bin/release-deb
+COPY deb-scripts/get-component.sh /usr/bin/get-component
+COPY deb-scripts/repo-cron.sh /usr/bin/repo-cron
+
+RUN adduser signald
+USER signald
+RUN gpg --no-default-keyring --keyring trustedkeys.gpg --import /tmp/apt-signing-key.asc