fix build breakage on windows

Reviewed-by: Tim Hudson <tjh@openssl.org>
diff --git a/apps/rehash.c b/apps/rehash.c
index b26cbf2..672a42a 100644
--- a/apps/rehash.c
+++ b/apps/rehash.c
@@ -441,6 +441,9 @@
 }
 
 #else
+OPTIONS rehash_options[] = {
+    {NULL}
+};
 
 int rehash_main(int argc, char **argv)
 {