Move the dummy source set from play to license gradle scripts so we don't need to do overrides internally (#713)

gradle/scripts/license.gradle

@@ -14,4 +14,15 @@ subprojects {
     excludes(["**/*.json", "**/*.avsc", "**/*.avro", "**/*.conf", "**/*.yaml", "**/*.xml"])
     excludes(["**/*.txt", "**/*.csv", "**/*.md"])
   }
+
+  plugins.withType(PlayPlugin) {
+    // Manually define a dummy sourceSet for license checking
+    sourceSets {
+      license {
+        java {
+          srcDirs = ['app', 'test']
+        }
+      }
+    }
+  }
 }

gradle/scripts/play.gradle

@@ -4,15 +4,6 @@ tasks.withType(PlayRun) {
     httpPort = project.ext.httpPort
 }
 
-// Manually define a sourceSet for license checking
-sourceSets {
-  license {
-    java {
-        srcDirs = ['app', 'test']
-    }
-  }
-}
-
 model {
     components {
         play {