Using `Environment.CurrentDirectory` for storing / reading files is dangerous as the current directory is mutable and can be changed when performing a certain operation (like opening solutions in roslyn type reference builder for example).
While it was nice having less projects to deal with, it meant hacks to get around circular dependencies between rulesets and osu.Game. For now, let's just restore the osu.Desktop project and call it a day.
This allows for the project to build again with default visual studio settings.