Make pipelines auto-interruptible by default

Fixes: KartKrew/Kart#1405

.gitlab-ci.yml

@@ -2,6 +2,10 @@ include:
   - '.gitlab/ci/templates/*.yml'
   - '.gitlab/ci/jobs/*.yml'
 
+workflow:
+  auto_cancel:
+    on_new_commit: interruptible
+
 variables:
   GIT_CLONE_PATH: $CI_BUILDS_DIR/$CI_CONCURRENT_ID/$CI_PROJECT_PATH
   GIT_DEPTH: 20
@@ -10,5 +14,6 @@ stages:
   - build
 
 default:
+  interruptible: true
   artifacts:
     expire_in: 1 day