ci don't run workflows twice on PRs

.github/workflows/arduino.yml

@@ -6,6 +6,7 @@ on:
     branches: [ master, release/v8.* ]
 jobs:
   lint:
+    if: ${{ github.event_name != 'pull_request' || github.repository != github.event.pull_request.head.repo.full_name }}
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2