Ugh, after download and unpack the version number on the NuGet package is 2017.07.20170710.01 (note one 0, not two). So that’s the string that needs to go in the download script and build.cs. Would be nice if this were consistent…
Side note: I’m a bit concerned that you still need to make the adjustment for PDBCopy - does WindowsExports.TryGetVSInstallDir not already report “E:\Program Files\Microsoft Visual Studio\2017\Community” in your environment?