Added missing license header in build-version.py

bazel/build-version.py

@@ -1,4 +1,17 @@
 #!/usr/bin/env python3
+# Copyright 2020-2021 The Verible Authors.
+#
+# 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.
 """
 Invoke bazel with --workspace_status_command=bazel/build-version.py to
 get this invoked and populate bazel-out/volatile-status.txt