fix failures found by randomconfig builds

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

libbb/nuke_str.c

@@ -0,0 +1,21 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Utility routines.
+ *
+ * Copyright (C) 2008 Denys Vlasenko
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+
+//kbuild:lib-y += nuke_str.o
+
+#include "libbb.h"
+
+void FAST_FUNC nuke_str(char *str)
+{
+        if (str) {
+		while (*str)
+			*str++ = 0;
+		/* or: memset(str, 0, strlen(str)); - not as small as above */
+	}
+}