There are a few inaccuracies there. For one thing, ninja automatically makes command lines the equivalent of input edges so that if the command line changes, 
the target will be rebuilt (except for generator=1 targets, which should only be the build.ninja file itself). So we don't need to do anything special to make sure that
 things get rebuilt in that case. It also sorta-kinda makes everything that the build.ninja task depends on have an order-only edge on build.ninja implicitly 
(really, if the build.ninja needs to be updated, it will do that first and reparse (repeatedly) before scheduling anything that isn't on the path to regenerating build.ninja).