Fix missing #include.

--- hfsutils-3.2.6/hpwd.c	1998-04-11 09:26:59.000000000 +0100
+++ hfsutils-3.2.6/hpwd.c	2025-07-03 17:50:32.848820531 +0100
@@ -24,6 +24,7 @@
 # endif
 
 # include <stdio.h>
+# include <string.h>
 
 # include "hfs.h"
 # include "hcwd.h"