#242: Cancel previous builds

Author: raymondschouten

.github/workflows/build.yaml

@@ -3,6 +3,10 @@ name: 'Build'
 on:
   push:
 
+concurrency:
+  group: "${{ github.workflow }}-${{ github.head_ref || github.run_id }}"
+  cancel-in-progress: true
+
 jobs:
   phpunit:
     name: 'PHPUnit'