dont bother defining _GNU_SOURCE

test/unistd/tst-preadwrite.c

@@ -18,7 +18,6 @@
    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
    02111-1307 USA.  */
 
-#define _GNU_SOURCE
 #include <stdlib.h>
 #include <stdio.h>
 #include <search.h>