Add fnl build target

mojo/tools/embed/rules.gni

 # 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.
 
 template("embed_file") {
   assert(defined(invoker.variable))
   assert(defined(invoker.source))
   assert(defined(invoker.namespace))
 
   variable = invoker.variable
@@ skipping 17 matching lines @@
     ]
 
     if (defined(invoker.testonly)) {
       testonly = invoker.testonly
     }
     if (defined(invoker.deps)) {
       deps = invoker.deps
     }
   }
 
+  config_target_name = "__${target_name}_config"
+  config(config_target_name) {
+    cflags = [ "-Wno-narrowing" ]
+  }
+
   source_set(target_name) {
     sources = generator_outputs
 
     if (defined(invoker.testonly)) {
       testonly = invoker.testonly
     }
 
+    configs += [ ":${config_target_name}" ]
+
     deps = [
       ":${generator_target_name}",
     ]
   }
 }