Add header missing from 9391a97

I had not noticed the new file after rebasing this commit on top
of e1b4c8c.

Author: PhilippWendler

c/pthread/reorder_5.i

@@ -1,3 +1,11 @@
+// This file is part of the SV-Benchmarks collection of verification tasks:
+// https://github.com/sosy-lab/sv-benchmarks
+//
+// SPDX-FileCopyrightText: 2011-2020 The SV-Benchmarks community
+// SPDX-FileCopyrightText: The ESBMC project
+//
+// SPDX-License-Identifier: Apache-2.0
+
 extern void abort(void);
 extern void __assert_fail(const char *, const char *, unsigned int, const char *) __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__noreturn__));
 void reach_error() { __assert_fail("0", "reorder_5.c", 3, "reach_error"); }