Don't try to seperate the dev/non-dev image builds

The dev image build uses the prod image build as a base. It doesn't
make sense to seperate them as they need to be sequential, and the
fastest way to do them is to re-use the environment from the first build

.gitlab-ci.yml

@@ -61,6 +61,10 @@ build_2019_image:
     - docker pull "${CONTAINER_IMAGE_2019}":latest || true
     - docker build --cache-from "${CONTAINER_IMAGE_2019}":latest -f docker/Dockerfile -t "${CONTAINER_IMAGE_2019}":$CI_COMMIT_SHA .
     - docker push "${CONTAINER_IMAGE_2019}":$CI_COMMIT_SHA
+    - docker build --build-arg CI_COMMIT_SHA=$CI_COMMIT_SHA -f docker/Dockerfile.dev -t "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_SHA .
+    - docker push "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_SHA
+    - docker tag "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_SHA "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_REF_SLUG
+    - docker push "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_REF_SLUG
   except:
     - "2019"
     - "dev/2019"
@@ -81,21 +85,6 @@ build_2019_image:
     name: 2019/prod
     url: https://2019.linux.conf.au
 
-build_2019_dev_image:
-  image: docker:git
-  stage: build
-  services:
-  - docker:dind
-  script:
-    - docker login -u _json_key -p "$GOOGLE_KEY" https://asia.gcr.io
-    - docker pull "${CONTAINER_IMAGE_2019}"_dev:latest || true
-    - docker build --cache-from "${CONTAINER_IMAGE_2019}"_dev:latest --build-arg CI_COMMIT_SHA=$CI_COMMIT_SHA -f docker/Dockerfile.dev -t "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_SHA .
-    - docker push "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_SHA
-    - docker tag "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_SHA "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_REF_SLUG
-    - docker push "${CONTAINER_IMAGE_2019}"_dev:$CI_COMMIT_REF_SLUG
-  except:
-    - master
-
 2019_dev-deploy:
   image: google/cloud-sdk
   stage: deploy