To ensure updating settings everytime settings.json is updated, we should do:
`settings: profile/settings.json`
And then, instead of `$@` or `profiles/settings.json` we can use `$<` to refer to first `settings` rule dependencies (i.e. `profile/settings.json`):
`python build/settings.py $(SETTINGS_ARG) --locale $(GAIA_DEFAULT_LOCALE) --hidpi --homescreen $(SCHEME)homescreen.$(GAIA_DOMAIN)$(GAIA_PORT)/manifest.webapp --ftu $(SCHEME)communications.$(GAIA_DOMAIN)$(GAIA_PORT)/manifest.webapp --wallpaper build/wallpaper@2x.jpg --override $(SETTINGS_PATH) --output $<`