Change task for building modules directory in distributions to sync.

This handles when dependencies have changed, so old ones will be
removed.

distribution/build.gradle

@@ -47,7 +47,7 @@ ext.dependencyFiles = project(':core').configurations.runtime.copyRecursive().ex
  *                                  Modules                                  *
  *****************************************************************************/
 
-task buildModules(type: Copy) {
+task buildModules(type: Sync) {
   into 'build/modules'
 }