Make `robius-authentication` compile on Linux

[gianzellweger]

I understand that the Linux version for robius-authentication is not finished yet, but it would be nice if it at least compiled. Looking at code, it doesn't seem to big of an undertaking.

[tyreseluo]

Thanks for your comment. Yes, I am adding support for authentication on Linux. You can view this PR to track the latest development progress.

• Feature(authentication): add Linux support using zbus and polkit #5