Defining _POSIX_C_SOURCE to 0 will make time.h not create the clockid_t
typedef used by some functions in pthread.h.
The right approach here is to set it to 199309L, which creates the
typedef on FreeBSD and doesn't set __USE_UNIX98 or __USE_XOPEN2K on
glibc, which is what the test is actually testing.
https://bugzilla.gnome.org/show_bug.cgi?id=672406
/* Test case for bug 659866 */
-#define _POSIX_C_SOURCE 0
+#define _POSIX_C_SOURCE 199309L
#undef _GNU_SOURCE
#undef _XOPEN_SOURCE
#include <pthread.h>