You could also, as an employer, supply a pre-built development environment appliance for VirtualBox that already has your source and everything set up. Then a person just has to install VirtualBox, add the appliance, and boot it. I think there is even a way to get it where the person doesn't even have to install VirtualBox.

As an employer you could also allow access to a remote instance of a machine that is already set up and configured and the person can SSH/RDP into the box and do development there.

I'm thinking that there probably isn't going to be a clear cut, one size fits all answer to this, but I do think there are some good options in any case.