Add SPDX identifiers for REUSE compliance

Co-authored-by: Mat Sutcliffe <oktal3700@gmail.com>

scripts/lib/util.py

@@ -1,5 +1,8 @@
 #!/usr/bin/env python
 
+# SPDX-FileCopyrightText: Copyright (C) 2017 swift Project Community / Contributors
+# SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-swift-pilot-client-1
+
 from __future__ import print_function
 
 import itertools