ninja: make setup-hook.sh closer to setup.sh

Things changed in the Ninja setup-hook:
- Respect installFlags
- Automatically add checkPhase (can be disabled with dontUseNinjaCheck
  in the same way as dontUseNinjaBuild and dontUseNinjaInstall). Tests
  are only run when "ninja test" exists.
- Error in build phase when build.ninja is missing. We don’t have a
  way to fall back to other build methods, so it’s best to be very
  clear when we aren’t able to build with ninja
- Set -l flag to 1 when enableParallelBuilding is disabled