feat: Use buildx in CI

.gitlab-ci.yml

@@ -72,15 +72,16 @@ build_image_for_commit:
   needs:
     - fetch_asset_dependencies
     - fetch_application_dependencies
-  image: "docker:19.03.12"
+  image: "docker:20.10"
   only:
     - master
   services:
-    - name: docker:19.03.12-dind
+    - name: docker:20.10-dind
   script:
     - docker login "https://${CI_REGISTRY}" -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD
     - docker pull $CI_REGISTRY_IMAGE:latest || true
-    - docker buildx build --cache-from $CI_REGISTRY_IMAGE:latest -t $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA .
+    - export DOCKER_BUILDKIT=1
+    - docker build --cache-from $CI_REGISTRY_IMAGE:latest -t $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA --build-arg BUILDKIT_INLINE_CACHE=1 .
     - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
 
 deploy_to_tags:

Dockerfile

@@ -24,6 +24,7 @@ ADD ./apps/admin/mix.exs /root/app/apps/admin/
 ADD ./apps/app/mix.exs /root/app/apps/app/
 ADD ./apps/content/mix.exs /root/app/apps/content/
 ADD ./apps/core/mix.exs /root/app/apps/core/
+ADD ./deps /root/app/deps
 RUN mix deps.get
 RUN mix deps.compile