vtkPythonPackages: avoid CMP0054 warnings
vtkPythonPackages: avoid CMP0054 warnings

Change-Id: I7882bd5b76788c563ce9f663cc1305f20c2f177d

demarle/VTK,johnkit/vtk-dev,mspark93/VTK,johnkit/vtk-dev,hendradarwin/VTK,keithroe/vtkoptix,gram526/VTK,jmerkow/VTK,keithroe/vtkoptix,mspark93/VTK,ashray/VTK-EVM,msmolens/VTK,jmerkow/VTK,mspark93/VTK,jmerkow/VTK,gram526/VTK,SimVascular/VTK,candy7393/VTK,SimVascular/VTK,ashray/VTK-EVM,gram526/VTK,keithroe/vtkoptix,hendradarwin/VTK,msmolens/VTK,jmerkow/VTK,ashray/VTK-EVM,sumedhasingla/VTK,ashray/VTK-EVM,demarle/VTK,ashray/VTK-EVM,demarle/VTK,SimVascular/VTK,sankhesh/VTK,jmerkow/VTK,msmolens/VTK,SimVascular/VTK,demarle/VTK,demarle/VTK,demarle/VTK,msmolens/VTK,jmerkow/VTK,sumedhasingla/VTK,mspark93/VTK,johnkit/vtk-dev,candy7393/VTK,msmolens/VTK,keithroe/vtkoptix,sumedhasingla/VTK,sankhesh/VTK,gram526/VTK,gram526/VTK,hendradarwin/VTK,demarle/VTK,sankhesh/VTK,msmolens/VTK,keithroe/vtkoptix,hendradarwin/VTK,sumedhasingla/VTK,candy7393/VTK,ashray/VTK-EVM,mspark93/VTK,mspark93/VTK,demarle/VTK,keithroe/vtkoptix,johnkit/vtk-dev,candy7393/VTK,mspark93/VTK,sankhesh/VTK,SimVascular/VTK,candy7393/VTK,hendradarwin/VTK,gram526/VTK,keithroe/vtkoptix,SimVascular/VTK,msmolens/VTK,candy7393/VTK,msmolens/VTK,sumedhasingla/VTK,johnkit/vtk-dev,keithroe/vtkoptix,jmerkow/VTK,sumedhasingla/VTK,ashray/VTK-EVM,candy7393/VTK,gram526/VTK,ashray/VTK-EVM,hendradarwin/VTK,johnkit/vtk-dev,sumedhasingla/VTK,sankhesh/VTK,jmerkow/VTK,sumedhasingla/VTK,sankhesh/VTK,mspark93/VTK,SimVascular/VTK,sankhesh/VTK,johnkit/vtk-dev,SimVascular/VTK,sankhesh/VTK,candy7393/VTK,hendradarwin/VTK,gram526/VTK