Nightly build TESTS failing for extensions with dependencies to other scriptable modules

[jcfr (Jean Christophe Fillion Robin (Kitware))]

The issue are the following:

• For SlicerRT, the config file is located in the top-level directory but the extension build system set SlicerRT_DIR using

  ${dep}_DIR:PATH=${${dep}_BINARY_DIR}/${${dep}_BUILD_SUBDIRECTORY}")
  

  This means the call to find_package(SlicerRT) fails because it can’t find a config file and reset the variable SlicerRT_DIR

• For SlicerDevelopmentToolbox, there is no SlicerDevelopmentToolboxConfig.cmake file and as @lassoan suggested, it can easily be fixed adding include(${Slicer_EXTENSION_GENERATE_CONFIG}) in https://github.com/fbudin69500/SlicerDeveloperToolsForExtensions/blob/5ceceabbb3ae35a669309389aa34e596699ca058/CMakeLists.txt#L26