Prefix build variables used in separate repos with mojo_

mojo/services/navigation/public/interfaces/BUILD.gn

Index: mojo/services/navigation/public/interfaces/BUILD.gn
diff --git a/mojo/services/navigation/public/interfaces/BUILD.gn b/mojo/services/navigation/public/interfaces/BUILD.gn
index 5141680ccc6c36f4df3aa23fb7d2979f4accf6ac..19b9f8aa184858784dad5f0e3e8a84320b97766c 100644
--- a/mojo/services/navigation/public/interfaces/BUILD.gn
+++ b/mojo/services/navigation/public/interfaces/BUILD.gn
@@ -12,13 +12,13 @@ mojom("interfaces") {
 
   import_dirs = [ get_path_info("../../../", "abspath") ]
 
-  if (defined(network_service_root)) {
-    import_dirs += [ network_service_root ]
+  if (defined(mojo_network_service_root)) {
+    import_dirs += [ mojo_network_service_root ]
   } else {
-    network_service_root = "../../.."
+    mojo_network_service_root = "../../.."
   }
 
   deps = [
-    "$network_service_root/network/public/interfaces",
+    "$mojo_network_service_root/network/public/interfaces",
   ]
 }