rtcd.pl: add license header to generated files

Bug: aomedia:3525
Change-Id: I614056558fb5439b448342e0c01e53bd8da85585

build/make/rtcd.pl

@@ -212,7 +212,19 @@ sub filter {
 #
 sub common_top() {
   my $include_guard = uc($opts{sym})."_H_";
+  my @time = localtime;
+  my $year = $time[5] + 1900;
   print <<EOF;
+/*
+ *  Copyright (c) ${year} The WebM 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.
+ */
+
 // This file is generated. Do not edit.
 #ifndef ${include_guard}
 #define ${include_guard}