Include <unistd.h>, as we are otherwise missing definitions on some systems.

tests/test_patching.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <fcntl.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <sys/time.h>
 
 #include "library.h"
 #include "sandbox.h"
 #include "test_runner.h"
 
 
 extern "C" int my_getpid(void);
 extern char my_getpid_end[];
 
@@ skipping 106 matching lines @@
   check_patching_vsyscall((char *) my_vgetcpu, my_vgetcpu_end);
 
   StartSeccompSandbox();
   // glibc's sched_getcpu() could still succeed if it goes via the
   // vdso and just reads memory, but my_vgetcpu() is always redirected
   // through the sandbox's handler and is rejected.
   CHECK(my_vgetcpu(NULL, NULL, NULL) == -ENOSYS);
 }
 
 #endif