external rendering module compilation failure
https://gitlab.kitware.com/vtk/vtk/blob/master/Rendering/External/vtkExternalOpenGLCamera.cxx#L130
compilation fails with
error: class "vtkRenderer" has no member "GetIsPicking"
&& !ren->GetIsPicking())
after the picking refactor of 1eb083a8
also but we should have a dashboard with external rendering turned on.