Tests: Speed up RunCMake.include_directories test

Remove unnecessary language initializations.  Change the main
CMakeLists.txt project() call to specify NONE.  Use enable_language(CXX)
instead of project() in cases that need it to avoid enabling C too.
Merge topic 'test-speedup-RunCMake.include_directories' into next

00fefc49 Tests: Speed up RunCMake.include_directories test