gitlab-ci: always run the containers build

If the first time a fork was created, the job creating the containers was
manually cancelled, this would have left the fork unable to use the CI
(until the next automatic regeneration of the container).

Avoid this by always running the container-generation job, even though
99% of the time it will spin up, see that the container exists and shut
down.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>

.gitlab-ci.yml

@@ -29,9 +29,18 @@ stages:
   - build+test
 
 
+# When to automatically run the CI
+.ci-run-policy:
+  only:
+    - master
+    - merge_requests
+    - /^ci([-/].*)?$/
+
+
 # CONTAINERS
 
 containers:ubuntu:
+  extends: .ci-run-policy
   stage: containers-build
   image: docker:stable
   services:
@@ -52,21 +61,14 @@ containers:ubuntu:
       docker image push $UBUNTU_IMAGE && exit || true
     - docker build -t $UBUNTU_IMAGE -f .gitlab-ci/Dockerfile.ubuntu .
     - docker push $UBUNTU_IMAGE
-  only:
-    changes:
-      - .gitlab-ci.yml
-      - .gitlab-ci/Dockerfile.ubuntu
 
 
 # BUILD
 
 .build:
+  extends: .ci-run-policy
   image: $UBUNTU_IMAGE
   stage: build+test
-  only:
-    - master
-    - merge_requests
-    - /^ci([-/].*)?$/
   artifacts:
     when: on_failure
     untracked: true