COMP: Superbuild - PYTHON_EXECUTABLE is now passed to CTK inner build

SuperBuild.cmake

@@ -228,6 +228,7 @@ ExternalProject_Add(${proj}
     -DCTK_KWSTYLE_EXECUTABLE:FILEPATH=${CTK_KWSTYLE_EXECUTABLE}
     -DDCMTK_DIR:PATH=${DCMTK_DIR} # FindDCMTK expects DCMTK_DIR variable to be defined
     -DVTK_DIR:PATH=${VTK_DIR}     # FindVTK expects VTK_DIR variable to be defined
+    -DPYTHON_EXECUTABLE:FILEPATH=${PYTHON_EXECUTABLE}   # FindPythonInterp expects PYTHON_EXECUTABLE variable to be defined
     -DPYTHON_INCLUDE_DIR:PATH=${PYTHON_INCLUDE_DIR}     # FindPythonQt expects PYTHON_INCLUDE_DIR variable to be defined
     -DPYTHON_LIBRARY:FILEPATH=${PYTHON_LIBRARY}         # FindPythonQt expects PYTHON_LIBRARY variable to be defined
     -DPYTHONQT_INSTALL_DIR:PATH=${PYTHONQT_INSTALL_DIR} # FindPythonQt expects PYTHONQT_INSTALL_DIR variable to be defined