New command -iso_nowtime to set fixed timestamp for synthetic files

xorriso/xorriso_private.h

@@ -554,6 +554,12 @@ struct XorrisO { /* the global context of xorriso */
   */
  char all_file_dates[80];
 
+ /* Timestamp for ISO files which have no origin file on disk and thus
+    normally get time(NULL) as timestamps
+ */
+ int do_override_now_time;
+ time_t now_time_override;
+
 #ifdef Xorriso_with_libjtE
  /* Parameters and state of Jigdo Template Export environment */
  struct libjte_env *libjte_handle;