Added webrtc/audio/utility directory and empty GN target.

webrtc/audio/utility/BUILD.gn

Index: webrtc/audio/utility/BUILD.gn
diff --git a/webrtc/audio/utility/BUILD.gn b/webrtc/audio/utility/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..f6c62d53ef0a78dd6dd5ec207c21404f4562fd51
--- /dev/null
+++ b/webrtc/audio/utility/BUILD.gn
@@ -0,0 +1,11 @@
+# Copyright (c) 2016 The WebRTC 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 in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+import("../../build/webrtc.gni")
+
+group("utility") {
+}