use "glibc errno" trick not only for ash, but for entire busybox

(add/remove: 1/1 grow/shrink: 37/37 up/down: 139/-228)        Total: -89 bytes

util-linux/setarch.c

@@ -7,11 +7,6 @@
  * Licensed under GPL v2 or later, see file License for details.
 */
 
-#include <stdlib.h>
-#include <unistd.h>
-#include <string.h>
-#include <errno.h>
-#include <stdio.h>
 #include <sys/personality.h>
 
 #include "libbb.h"