Add LICENSE file and boilerplate.

for i in `find  ./ -regex ".*\.cuh?$"`
do
  sh -c "cat ~/boilerplate ${i} > tmp && mv tmp ${i}"
done

testing/cpu_timer.cu

@@ -1,3 +1,21 @@
+/*
+ *  Copyright 2020 NVIDIA Corporation
+ *
+ *  Licensed under the Apache License, Version 2.0 with the LLVM exception
+ *  (the "License"); you may not use this file except in compliance with
+ *  the License.
+ *
+ *  You may obtain a copy of the License at
+ *
+ *      http://llvm.org/foundation/relicensing/LICENSE.txt
+ *
+ *  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.
+ */
+
 #include <nvbench/cpu_timer.cuh>
 
 #include "test_asserts.cuh"