ci(ucslint): Use correct image

Only build the image when ucslint is touched.

Fallback to :latest otherwise.

Bug #55668

.gitlab-ci.yml

@@ -79,18 +79,27 @@ drop aptly:
     name: $CI_COMMIT_REF_NAME
     action: stop
 
-prepare ucslint:
+build ucslint:
   stage: prepare
-  interruptible: false
   extends: .kaniko
   variables:
     KANIKO_BUILD_CONTEXT: packaging/ucslint
     KANIKO_ARGS: --build-arg ucs=$ucs --cache=true
-    IMAGE_TAG: ""
   rules:
     - changes:
       - packaging/ucslint/**/*
 
+select ucslint:
+  stage: prepare
+  needs:
+    - job: build ucslint
+      optional: true
+  script:
+    - echo "UCSLINT=${IMAGE_TAG:-$CI_REGISTRY_IMAGE:latest}" | tee .env
+  artifacts:
+    reports:
+      dotenv: .env
+
 doc-pipeline:
   stage: build
   rules:
@@ -138,8 +147,9 @@ deb-pipeline:
   needs:
     - job: generate-config
     - job: prepare aptly
-    - job: prepare ucslint
-      optional: true
+    - job: select ucslint
+  variables:
+    UCSLINT: $UCSLINT
   trigger:
     include:
       - artifact: generated-config-deb.yml

.gitlab-ci/base-deb.yml

@@ -5,7 +5,7 @@ stages:
 .lint:
   stage: lint
   image:
-    name: $IMAGE_TAG
+    name: $UCSLINT
     entrypoint: [""]
   script:
     - ucslint -j ucslint.xml $base

.gitlab-ci/base.yml

@@ -21,4 +21,3 @@ variables:
   DEB: docker-registry.knut.univention.de/phahn/ucs-debbase:$ucs
   APTLY: http://omar.knut.univention.de:11620/api
   APT: http://omar.knut.univention.de/build2/git
-  IMAGE_TAG: $CI_REGISTRY_IMAGE