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

mojo/public/mojo.gni

-# 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("//build/module_args/dart.gni")
-import("//build/module_args/mojo.gni")
-
-# If using the prebuilt shell, gate its usage by the platforms for which it is
-# published.
-mojo_use_prebuilt_mojo_shell = false
-if (!defined(mojo_build_mojo_shell_from_source) ||
-    !mojo_build_mojo_shell_from_source) {
-  mojo_use_prebuilt_mojo_shell = is_linux || is_android
-}
-
-# If using the prebuilt dart_snapshotter, gate its usage by the platforms for
-# which it is published.
-mojo_use_prebuilt_dart_snapshotter = false
-if (!defined(mojo_build_dart_snapshotter_from_source) ||
-    !mojo_build_dart_snapshotter_from_source) {
-  mojo_use_prebuilt_dart_snapshotter = true
-} else {
-  assert(defined(dart_snapshotter_bin))
-}
-
-# If using the prebuilt network service, gate its usage by the platforms for
-# which it is published.
-mojo_use_prebuilt_network_service = false
-if (!defined(mojo_build_network_service_from_source) ||
-    !mojo_build_network_service_from_source) {
-  mojo_use_prebuilt_network_service = is_linux || is_android
-}
-
-# Enable Dart apptest framework by default.
-mojo_use_dart_apptest_framework = true
-if (defined(mojo_disable_dart_apptest_framework) &&
-    mojo_disable_dart_apptest_framework) {
-  mojo_use_dart_apptest_framework = false
-}
-
-# Embedder uses Mojo network interfaces.
-mojo_use_network_in_sdk = true
-if (defined(mojo_disable_network_in_sdk) && mojo_disable_network_in_sdk) {
-  mojo_use_network_in_sdk = false
-}
-
-# The absolute path to the directory containing the mojo public SDK (i.e., the
-# directory containing mojo/public). The build files within the Mojo public
-# SDK use this variable to allow themselves to be parameterized by the location
-# of the public SDK within a client repo.
-mojo_root = get_path_info("../..", "abspath")