message: Doc the optional-ness of kits
diff: @@ -29,6 +29,10 @@ MSBuild and .sln generator is used for the Visual C++ compiler.
  If you change the active Kit while a project is configured, the project
  configuration will be re-generated with the chosen kit.
  +.. note::
  + Using a kit is recommended but optional. Opting-out of using kits will
  + cause CMake to perform its own automatic detection.
  +
  How Are Kits Found and Defined?
  ===============================
  