title: Microsoft.TeamFoundation.Build.Client.BuildDetail error
body: <p>I have a TFS 2013 RC install running VS 19,12, and 13 on the build agents. I have a build definition using the CopyDirectory action from the toolbox and when I place anything other than a hard-coded path in either the source or destination box, I get this error
   The build process failed validation. Details: Validation Error: The private implementation of activity '1: DynamicActivity' has the following validation error:   Compiler error(s) encountered processing expression "BuildDetail.DropLocation".'Microsoft.TeamFoundation.Build.Client.BuildDetail' is not accessible in this context because it is 'Friend'.
  I have googled this and nothing seems to come up that works.
  Any ideas would be great, as we are blocked on using this.
  Thanks,
  Devin</p>