drone new stage test-android-build does one apk --debug build

.drone.yml

@@ -68,6 +68,16 @@ steps:
       - tar -czf cwtch-`cat ../VERSION`.tar.gz cwtch
       - rm -r cwtch
 
+  - name: test-build-android
+    image: cirrusci/flutter:dev
+    when: pull_request
+      event: 
+    volumes:
+      - name: deps
+        path: /root/.pub-cache
+    commands:
+      - flutter build apk --debug
+
   - name: build-android
     image: cirrusci/flutter:dev
     when: