SMTK: only support an external SMTK
Building SMTK as part of CMB still needs work from ParaView's side to allow SMTK to install properly on macOS. Since it does not work there, do not make it seem as if it is supported.
Cc: @dcthomp @bob.obara
Building SMTK as part of CMB still needs work from ParaView's side to allow SMTK to install properly on macOS. Since it does not work there, do not make it seem as if it is supported.
Cc: @dcthomp @bob.obara