Copy itk build script at the end of Dockerfile
Copy itk build script at the end of Dockerfile

This is to allow for faster testing, so cmake doesn't need to
be re-built very time the ITK build script changes.

Signed-off-by: Patrick Avery <743342299f279e7a8c3ff5eb40671fce3e95f13a@kitware.com>

OpenChemistry/tomviz-superbuild,cjh1/tomviz-superbuild,cjh1/tomviz-superbuild,OpenChemistry/tomviz-superbuild