Starting work on full GN build

.gn

Index: .gn
diff --git a/.gn b/.gn
new file mode 100644
index 0000000000000000000000000000000000000000..fc54abe46e96f5e95d02629b5d1b5360bd1effc7
--- /dev/null
+++ b/.gn
@@ -0,0 +1,14 @@
+# Copyright 2016 The Dart project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This file is used by the gn meta-buildsystem find the root of the source tree
+# and to set startup options.
+
+# The location of the build configuration file.
+buildconfig = "//build/config/BUILDCONFIG.gn"
+
+# The secondary source root is a parallel directory tree where
+# GN build files are placed when they can not be placed directly
+# in the source tree, e.g. for third party source trees.
+secondary_source = "//build/secondary/"