--- thirdparty/zlib/gzwrite.c.orig	2021-11-25 00:56:54 UTC
+++ thirdparty/zlib/gzwrite.c
@@ -4,6 +4,7 @@
  */
 
 #include "gzguts.h"
+#include <unistd.h>
 
 /* Local functions */
 local int gz_init OF((gz_statep));