add subprojects field

Author: SelaseKay

packages/firebase_snippets_app/android/build.gradle

@@ -19,6 +19,18 @@ allprojects {
         google()
         mavenCentral()
     }
+
+     subprojects {
+        afterEvaluate { project ->
+            if (project.hasProperty('android')) {
+                project.android {
+                    if (namespace == null) {
+                        namespace project.group
+                    }
+                }
+            }
+        }
+    }
 }
 
 rootProject.buildDir = '../build'