This hasn't been tested in years, and doesn't makes sense when you
consider other files are saved in the DataRoot directory (e.g. custom
properties, play time, crash dumps, etc).
-portable is redundant as the presence of settings.ini in the AppRoot
will trigger it anyway, therefore it is only relevant for first-time
installs. In which case it's just as much work to create an empty
settings.ini or portable.txt file as it is to create a shortcut with
-portable on the command line.
It was also broken anyway for a long time, and nobody complained.
