GN: Enable PNaCl plugin compilation for the key_tester app.

remoting/tools/javascript_key_tester/pnacl/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.
 
 assert(is_nacl,
        "These targets must only be built using the untrusted NaCl toolchains.")
 
-# TODO(sbc): Make sure this library gets built with -fPIC.  Right now it
-# doesn't seem that is built at all.
-source_set("ppapi_stub_lib") {
+executable("remoting_key_tester_newlib") {
   sources = [
-    "plugin_main_irt.c",
-    "ppapi_plugin_main.c",
-    "ppapi_plugin_start.c",
-    "thread_creator.c",
+    "remoting_key_tester.cc",
+  ]
+
+  deps = [
+    "//ppapi/native_client:ppapi_lib",
+    "//ppapi/cpp",
   ]
 }