Cancel previous CI run on new pull request push (#311)

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.github/workflows/android-ci-pull.yml

@@ -15,6 +15,9 @@ on:
 jobs:
   build:
     runs-on: ubuntu-20.04
+    concurrency: 
+      group: ${{ github.ref }}
+      cancel-in-progress: true
     defaults:
       run:
         working-directory: platform/android