okey figured out whats the problem.
In 3rd_party folder, there is Steamworks which should only contain Steamworks.build.cs if you dont want to build with Steamworks support. So delete the others file (a folder which contain compiled sdk, called Steamv130). If you delete it, then the UE4 builder will set a boolean to false indicating you dont want to use steam and will not compile the offending cpps.
These files are included in Required_2of3.zip and I think they should be deleted …