gitlab: Use plain docker in container-template.yml

Our dockerfiles no longer reference layers from other qemu images so
we can now use 'docker build' on them.

Also reinstate the caching that was disabled due to bad interactions
with certain runners. See commit 6ddc3dc7a8 ("tests/docker: don't use
BUILDKIT in GitLab either"). We now believe those issues to be fixed.

The COMMON_TAG needed to be fixed for the caching to work. The
docker.py script was not using the variable, but constructing the
correct URL directly.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Tested-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20230227151110.31455-2-farosas@suse.de>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230228190653.1602033-16-alex.bennee@linaro.org>

.gitlab-ci.d/container-template.yml

@@ -6,17 +6,16 @@
     - docker:dind
   before_script:
     - export TAG="$CI_REGISTRY_IMAGE/qemu/$NAME:latest"
-    - export COMMON_TAG="$CI_REGISTRY/qemu-project/qemu/$NAME:latest"
+    - export COMMON_TAG="$CI_REGISTRY/qemu-project/qemu/qemu/$NAME:latest"
     - apk add python3
     - docker info
     - docker login $CI_REGISTRY -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD"
   script:
     - echo "TAG:$TAG"
     - echo "COMMON_TAG:$COMMON_TAG"
-    - ./tests/docker/docker.py --engine docker build
-          -t "qemu/$NAME" -f "tests/docker/dockerfiles/$NAME.docker"
-          -r $CI_REGISTRY/qemu-project/qemu
-    - docker tag "qemu/$NAME" "$TAG"
+    - docker build --tag "$TAG" --cache-from "$TAG" --cache-from "$COMMON_TAG"
+      --build-arg BUILDKIT_INLINE_CACHE=1
+      -f "tests/docker/dockerfiles/$NAME.docker" "."
     - docker push "$TAG"
   after_script:
     - docker logout