cmake: depend on ninja
cmake: depend on ninja

We change the default generator to ninja, so we should also
make sure it is always available.

Fixes #11620

Alexpux/MINGW-packages,fabiangreffrath/MINGW-packages,oscarfv/MINGW-packages,oscarfv/MINGW-packages,Alexpux/MINGW-packages,JPeterMugaas/MINGW-packages,JPeterMugaas/MINGW-packages,lhmouse/MINGW-packages,Alexpux/MINGW-packages,lhmouse/MINGW-packages,JPeterMugaas/MINGW-packages,fabiangreffrath/MINGW-packages,fabiangreffrath/MINGW-packages,oroppas/MINGW-packages,JPeterMugaas/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,stahta01/MINGW-packages,Alexpux/MINGW-packages,fabiangreffrath/MINGW-packages,lhmouse/MINGW-packages,JPeterMugaas/MINGW-packages,Alexpux/MINGW-packages,stahta01/MINGW-packages,oroppas/MINGW-packages,oscarfv/MINGW-packages,lhmouse/MINGW-packages,oroppas/MINGW-packages,stahta01/MINGW-packages,fabiangreffrath/MINGW-packages,stahta01/MINGW-packages,lhmouse/MINGW-packages,oscarfv/MINGW-packages,lhmouse/MINGW-packages,fabiangreffrath/MINGW-packages,oroppas/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,oroppas/MINGW-packages,JPeterMugaas/MINGW-packages,oroppas/MINGW-packages,Alexpux/MINGW-packages