Anthony,
I have no idea what is this error about.
Did you try to build it from unzipped archive you downloaded? I guess that in this case you need to clone git repository from github, and then try building from local repo. This git command is probably trying to retireve commit hash which in your case is unavailable, because there's no such information in unzipped content.
Also, what exactly are you expecting to get by building against Master.proj? This file does a lot of things, and is probably used mainly by project maintainers. For you local needs you may probably just open solution file with Visual Studio, or run msbuild command against solution file only.