ENH: Propagate CMAKE_CONFIGURATION_TYPES to all external projects

This allows to configure CTK and all dependent projects so that only
configuration is presented to the user.

This can be done by explicitly settings -DCMAKE_CONFIGURATION_TYPES:STRING=Release

CMakeLists.txt

@@ -85,6 +85,8 @@ if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
 endif()
 if(NOT CMAKE_CONFIGURATION_TYPES)
   mark_as_superbuild(VARS CMAKE_BUILD_TYPE ALL_PROJECTS)
+else()
+  mark_as_superbuild(VARS CMAKE_CONFIGURATION_TYPES ALL_PROJECTS)
 endif()
 
 mark_as_superbuild(