Make the fuchsia mojo/public repo the source of truth.

mojo/public/build/config/BUILD.gn

-# 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")
-
-config("mojo_sdk") {
-  include_dirs = [
-    # Include paths in the Mojo public SDK are specified relative to the
-    # directory holding the SDK.
-    mojo_root,
-
-    # The same goes for files generated from mojoms.
-    root_gen_dir + mojo_root,
-
-    # Mojo C headers should be included as <mojo/...>. The
-    # mojo/public/c:c_config config theoretically makes this work, but this
-    # requires that everyone use public_deps correctly (in order to propagate
-    # the config).
-    # TODO(vtl): Try to fix everyone, so that this isn't necessary. (That, or
-    # consider using all_dependent_configs instead.
-    "$mojo_root/mojo/public/c/include",
-  ]
-}