Limit the master-only rule to joerick/cibuildwheel

.github/workflows/test.yml

@@ -1,15 +1,16 @@
 name: Test
 
 on:
-  push:
-    branches:
-      - master
+  push: {}
   pull_request:
     paths-ignore:
       - 'docs/**'
 
 jobs:
   test:
+    # skip branch builds on joerick/cibuildwheel, but always build `master` and pull requests
+    if: github.repository != 'joerick/cibuildwheel' || github.ref == 'refs/heads/master' || github.event_name == 'pull_request'
+
     name: Test cibuildwheel on ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
     strategy: