diff -u liolib.c.orig liolib.c 
--- liolib.c.orig	2020-10-04 12:06:03.579772529 +0200
+++ liolib.c	2020-10-04 12:12:12.061843306 +0200
@@ -16,6 +16,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#if defined(HAVE_UNISTD_H)
+#include <unistd.h>
+#endif
 
 #include "lua.h"
 
