[PATCH] gitlab-ci: Replace Docker with Kaniko

[Camilla Conte <cconte@redhat.com>]

Enables caching from the qemu-project repository.

Uses a dedicated "$NAME-cache" tag for caching, to address limitations.
See issue "when using --cache=true, kaniko fail to push cache layer [...]":
https://github.com/GoogleContainerTools/kaniko/issues/1459

Does not specify a context since no Dockerfile is using COPY or ADD instructions.

Does not enable reproducible builds as
that results in builds failing with an out of memory error.
See issue "Using --reproducible loads entire image into memory":
https://github.com/GoogleContainerTools/kaniko/issues/862

Previous attempts, for the records:
  - Alex Bennée: https://lore.kernel.org/qemu-devel/20230330101141.30199-12-alex.bennee@linaro.org/
  - Camilla Conte (me): https://lore.kernel.org/qemu-devel/20230531150824.32349-6-cconte@redhat.com/

Signed-off-by: Camilla Conte <cconte@redhat.com>
---
 .gitlab-ci.d/container-template.yml | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/.gitlab-ci.d/container-template.yml b/.gitlab-ci.d/container-template.yml
index 4eec72f383..066f253dd5 100644
--- a/.gitlab-ci.d/container-template.yml
+++ b/.gitlab-ci.d/container-template.yml
@@ -1,21 +1,18 @@
 .container_job_template:
   extends: .base_job_template
-  image: docker:latest
   stage: containers
-  services:
-    - docker:dind
+  image:
+    name: gcr.io/kaniko-project/executor:debug
+    entrypoint: [""]
+  variables:
+    DOCKERFILE: "$CI_PROJECT_DIR/tests/docker/dockerfiles/$NAME.docker"
+    CACHE_REPO: "$CI_REGISTRY/qemu-project/qemu/qemu/$NAME-cache"
   before_script:
     - export TAG="$CI_REGISTRY_IMAGE/qemu/$NAME:$QEMU_CI_CONTAINER_TAG"
-    # Always ':latest' because we always use upstream as a common cache source
-    - export COMMON_TAG="$CI_REGISTRY/qemu-project/qemu/qemu/$NAME:latest"
-    - docker login $CI_REGISTRY -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD"
-    - until docker info; do sleep 1; done
   script:
     - echo "TAG:$TAG"
-    - echo "COMMON_TAG:$COMMON_TAG"
-    - docker build --tag "$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
+    - /kaniko/executor
+      --dockerfile "$DOCKERFILE"
+      --destination "$TAG"
+      --cache=true
+      --cache-repo="$CACHE_REPO"
-- 
2.45.0