Add initial prototype for the GN meta-buildsystem.

tools/gn/secondary/third_party/modp_b64/BUILD.gn

Index: tools/gn/secondary/third_party/modp_b64/BUILD.gn
diff --git a/build/android/pylib/uiautomator/__init__.py b/tools/gn/secondary/third_party/modp_b64/BUILD.gn
similarity index 58%
copy from build/android/pylib/uiautomator/__init__.py
copy to tools/gn/secondary/third_party/modp_b64/BUILD.gn
index cda7672a8d06dd3d79480cf415e1d37470f638a3..5598f12f18209f028e7108ac5a9101e99343854c 100644
--- a/build/android/pylib/uiautomator/__init__.py
+++ b/tools/gn/secondary/third_party/modp_b64/BUILD.gn
@@ -1,4 +1,11 @@
-# Copyright (c) 2013 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.
-
+# Copyright (c) 2013 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.
+
+static_library("modp_b64") {
+  sources = [
+    "modp_b64.cc",
+    "modp_b64.h",
+    "modp_b64_data.h",
+  ]
+}