Sometimes Visual Studio is installed into a custom location, or the
user wants to specifically select a particular Visual Studio
installation when there are many installed.

You can set the `vs_install_path` and `vs_install_version` config
variables to override the automatic detection of the Visual Studio
installation location. F.ex., in `~/.cerbero/cerbero.cbc`

This is needed for running Cerbero on the Windows CI, where we use
Visual Studio Build Tools 2019 installed in `C:\BuildTools`.