check release: add license header

Author: 0xc0170

tools/check_release.py

@@ -1,3 +1,21 @@
+"""
+Copyright (c) 2016 ARM Limited. All rights reserved.
+
+SPDX-License-Identifier: Apache-2.0
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
 # Script to check a new mbed 2 release by compiling a set of specified test apps 
 # for all currently supported platforms. Each test app must include an mbed library.
 # This can either be the pre-compiled version 'mbed' or the source version 'mbed-dev'.