Merge pull request #494 from unpoller/fix-public-pull-requests-ci

fixes public pull requests CI to actually run

.github/workflows/build.yml

@@ -1,11 +1,14 @@
 name: Build
 
-on: [push]
+on: 
+  - pull_request
 
 permissions:
   contents: read
-  # Optional: allow read access to pull request. Use with `only-new-issues` option.
-  # pull-requests: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 
 jobs:
   test: