Add a doc pointer for internal users.

Test: N/A
Change-Id: I316ab1cc7b6272eee1d6ed88bfade1e18a6475e2
diff --git a/build/README.md b/build/README.md
index 22726ee..3e577bb 100644
--- a/build/README.md
+++ b/build/README.md
@@ -31,7 +31,7 @@
 
     See the [Android source access
     instructions](https://source.android.com/setup/build/downloading) for
-    further details.
+    further details. Google internal users please see [go/sync](http://go/sync).
 
 2.  Set up the development environment: