busybox: add 1.18.2 libbb fix

--- busybox-1.18.2/libbb/vfork_daemon_rexec.c

+++ busybox-1.18.2-libbb/libbb/vfork_daemon_rexec.c

@@ -52,6 +52,7 @@ pid_t FAST_FUNC spawn(char **argv)

 	 * Interested party can wait on pid and learn exit code.

 	 * If 111 - then it (most probably) failed to exec */

 	if (failed) {

+		safe_waitpid(pid, NULL, 0); /* prevent zombie */

 		errno = failed;

 		return -1;

 	}