Merge topic 'chem_ogl2_fix'

63417cca

 make the opengl2 module required for the backend
Acked-by: Kitware Robot <kwrobot@kitware.com>
Reviewed-by: Berk Geveci <berk.geveci@kitware.com>
Merge-request: !1177

Domains/ChemistryOpenGL2/module.cmake

@@ -7,6 +7,7 @@ vtk_module(vtkDomainsChemistryOpenGL2
     vtkDomainsChemistry
   BACKEND
     OpenGL2
+  IMPLEMENTATION_REQUIRED_BY_BACKEND
   PRIVATE_DEPENDS
     vtkglew
   KIT