Add missing license headers

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@258196 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/compiler.py

@@ -1,3 +1,12 @@
+#===----------------------------------------------------------------------===##
+#
+#                     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.
+#
+#===----------------------------------------------------------------------===##
+
 import os
 import lit.util
 import libcxx.util