ci: Add a job to trigger a cerbero build, similar to the monorepo

This should help prevent breakage like cerbero!1418 (merged).

.gitlab-ci.yml

@@ -20,6 +20,8 @@ variables:
   # to ensure that we are testing against the same thing as GStreamer itself.
   # The tag name is included above from the main repo.
   GSTREAMER_DOC_IMAGE: "registry.freedesktop.org/gstreamer/gstreamer/amd64/fedora:$FEDORA_TAG-main"
+  # Use the gstreamer image to trigger the cerbero job, same as the monorepo
+  CERBERO_TRIGGER_IMAGE: "registry.freedesktop.org/gstreamer/gstreamer/amd64/fedora:$FEDORA_TAG-main"
   WINDOWS_BASE: "registry.freedesktop.org/gstreamer/gstreamer-rs/windows"
   WINDOWS_RUST_MINIMUM_IMAGE: "$WINDOWS_BASE:$GST_RS_IMG_TAG-main-$GST_RS_MSRV"
   WINDOWS_RUST_STABLE_IMAGE: "$WINDOWS_BASE:$GST_RS_IMG_TAG-main-$GST_RS_STABLE"
@@ -385,25 +387,21 @@ coverage:
         coverage_format: cobertura
         path: coverage.xml
 
-# XXX: Copied from gstreamer monorepo, keep in sync
 cerbero trigger:
-  timeout: '4h'
-  extends:
-    - '.debian:12-stable'
+  image: $CERBERO_TRIGGER_IMAGE
   needs: [ "trigger" ]
   variables:
     # We will build this cerbero branch in the cerbero trigger CI
     CERBERO_UPSTREAM_BRANCH: 'main'
   script:
-    - pip3 install python-gitlab --break-system-packages # TEMPORARY HACK
     - ci/cerbero/trigger_cerbero_pipeline.py
   rules:
     # Never run post merge
     - if: '$CI_PROJECT_NAMESPACE == "gstreamer"'
       when: never
-    - changes:
-      when: never
-      - "LICENSE*"
+    # Don't run if the only changes are files that cargo-c does not read
+    - if:
+      changes:
       - "CHANGELOG.md"
       - "README.md"
       - "deny.toml"
@@ -417,3 +415,5 @@ cerbero trigger:
       - "**/meson.build"
       - "ci/*.sh"
       - "ci/*.py"
+      when: never
+    - when: always