fix !ENABLE_FEATURE_GETOPT_LONG build. Closes 3775

When compiling with !ENABLE_FEATURE_GETOPT_LONG, busybox still tries
to include getopt.h which is not available; for example with uClibc
when !UCLIBC_HAS_GETOPT_LONG.  getopt.h is only required
for the _long set of functions.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

libbb/getopt32.c

@@ -7,7 +7,9 @@
  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
 
-#include <getopt.h>
+#if ENABLE_LONG_OPTS || ENABLE_FEATURE_GETOPT_LONG
+# include <getopt.h>
+#endif
 #include "libbb.h"
 
 /*      Documentation