[Upgrade 4.15 to 4.16] Build.cs - How can I get engine directory

I’m trying to upgrade my 4.15 project to 4.16 (and eventually to 4.17) but I can’t find a good replacement for

UnrealBuildTool.UnrealBuildTool.EngineSourceDirectory

in my Build.cs file. I found

AutomationTool.CommandUtils.EngineDirectory

but when I put

using AutomationTool; 

at the top of my Build.cs file, Generate Visual Studio Project Files fails saying

BaseVR.Build.cs(4,7) : error CS0246:
The type or namespace name
‘AutomationTool’ could not be found
(are you missing a using directive or
an assembly reference?)

I could obviously make an Environment Variable with the path to that location, but then I have go through every coworker’s machine and set that. Is there a way in 4.16 to just get either engine or source directory? UnreaBuildTool class was made protected in 4.16 - it was public in 4.15. All that information is still there, but now I can’t access it.

DirectoryReference.GetCurrentDirectory()

points to current engine’s source folder, Program Files\Epic Games\UE_4.17\Engine\Source in my case