Build skyx packages by default

sky/services/activity/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 group("activity") {
   testonly = true
 
   deps = [
     ":interfaces",
   ]
 
   if (is_android) {
     deps += [ ":activity_lib" ]
   }
 }
 
+mojom("interfaces") {
+  sources = [
+    "activity.mojom",
+  ]
+}
+
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
 
   android_library("activity_lib") {
     java_files = [ "src/org/domokit/activity/ActivityImpl.java" ]
 
     deps = [
       "//base:base_java",
       "//mojo/public/java:bindings",
       "//mojo/public/java:system",
       ":interfaces_java",
     ]
   }
 }
-
-mojom("interfaces") {
-  sources = [
-    "activity.mojom",
-  ]
-}