Unreal Engine 4 is available for Win10 UWP app dev now

I’m trying to build latest uwp branch and there is an error:

EXEC : error : System.ArgumentException: An item with the same key has already been added.
9> at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
9> at System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add) 9> at UnrealBuildTool.UEBuildTarget.Build(BuildConfiguration BuildConfiguration, CPPHeaders Headers, List1 OutputItems, List`1 UObjectModules, ActionGraph ActionGraph) in C:\Data\MICROSOFT_UWP_UNREAL\Engine\Source\Programs\UnrealBuildTool\Configuration\UEBuildTarget.cs:line 2403
9> at UnrealBuildTool.UnrealBuildTool.RunUBT(BuildConfiguration BuildConfiguration, String] Arguments, FileReference ProjectFile) in C:\Data\MICROSOFT_UWP_UNREAL\Engine\Source\Programs\UnrealBuildTool\System\UnrealBuildTool.cs:line 1396
9>C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V140\Microsoft.MakeFile.Targets(41,5): error MSB3075: The command “…..\Build\BatchFiles\Build.bat UE4Editor Win64 Development -waitmutex” exited with code 5. Please verify that you have sufficient rights to run this command.