ci: cancel previous workflow run on new commit (#7619)

.github/workflows/arduino.yml

@@ -4,6 +4,13 @@ on:
     branches: [ master, release/v8.* ]
   pull_request:
     branches: [ master, release/v8.* ]
+
+# https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#concurrency
+# Ensure that only one commit will be running tests at a time on each PR
+concurrency:
+  group: ${{ github.ref }}-${{ github.workflow }} 
+  cancel-in-progress: true
+
 jobs:
   lint:
     if: ${{ github.event_name != 'pull_request' || github.repository != github.event.pull_request.head.repo.full_name }}