Only do one build at a time. Cancel older in progress builds.

Author: rouilj

.github/workflows/ci-test.yml

@@ -19,6 +19,10 @@ on:
 permissions:
   contents: read
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+    cancel-in-progress: true
+
 jobs:
   test:
     name: CI build test