ci: Cancel running jobs

No need to have parallel pipelines when updating a job.

Part-of: <https://gitlab.gnome.org/World/Phosh/squeekboard/-/merge_requests/619>

.gitlab-ci.yml

@@ -1,5 +1,19 @@
 image: debian:bookworm
 
+default:
+  # Protect CI infra from rogue jobs
+  timeout: 15 minutes
+  # Allow jobs to be caneled on new commits
+  interruptible: true
+  # Retry on infra hickups automatically
+  retry:
+    max: 1
+    when:
+      - api_failure
+      - runner_system_failure
+      - scheduler_failure
+      - stuck_or_timeout_failure
+
 stages:
   - build
   - test