Adjust folder to instal guest additions in windows guest

[caspertone]

I decided to install Guest Additions in a different folder location than the default one. So far, so good.
Every time I update VBox, I need to reinstall also GA. But it always insists in installing to the default directory, not checking if there is already a different installation folder.

I suggest to include in the GA installer the smartness to use an already selected user folder....

Thanks