Revert "Update aosp/master libcxx rebase to r263688"

The world is burning.

This reverts commit c004fd909c, reversing
changes made to 1418e4163d.

test/libcxx/util.py

@@ -1,12 +1,3 @@
-#===----------------------------------------------------------------------===##
-#
-#                     The LLVM Compiler Infrastructure
-#
-# This file is dual licensed under the MIT and the University of Illinois Open
-# Source Licenses. See LICENSE.TXT for details.
-#
-#===----------------------------------------------------------------------===##
-
 from contextlib import contextmanager
 import os
 import tempfile