Rearrange mojo/nacl files.

mojo/public/platform/nacl/BUILD.gn

Index: mojo/public/platform/nacl/BUILD.gn
diff --git a/mojo/public/platform/nacl/BUILD.gn b/mojo/public/platform/nacl/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..7b4fb2de5b090bf942e7ae9ea85953e3cbc7c95c
--- /dev/null
+++ b/mojo/public/platform/nacl/BUILD.gn
@@ -0,0 +1,17 @@
+# Copyright 2014 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_sdk.gni")
+
+# Untrusted code
+if (is_nacl) {
+  # Thunk mapping the Mojo public API onto NaCl syscalls.
+  mojo_sdk_source_set("mojo") {
+    sources = [
+      "libmojo.cc",
+      "mojo_irt.h",
+    ]
+    mojo_sdk_deps = [ "mojo/public/c/system" ]
+  }
+}