Add missing include to gtk scaffolding

Without unistd access, close and unlink were not properly defined

gtk/scaffolding.c

@@ -22,6 +22,7 @@
 #include <stdio.h>
 #include <errno.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <gtk/gtk.h>
 #include <gdk-pixbuf/gdk-pixbuf.h>