Add support for compiling V8 standalone using gn

build/module_args/v8.gni

Index: build/module_args/v8.gni
diff --git a/build/module_args/v8.gni b/build/module_args/v8.gni
new file mode 100644
index 0000000000000000000000000000000000000000..94af3a4ff703cc2e6be5072ae6ee742f1166e597
--- /dev/null
+++ b/build/module_args/v8.gni
@@ -0,0 +1,12 @@
+# Copyright 2015 The V8 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.
+
+import("//build/config/features.gni")
+import("//build/config/ui.gni")
+
+if (is_android) {
+  import("//build/config/android/config.gni")
+}
+
+v8_use_external_startup_data = false