If a typo is made in passing in arguments, earth should be able to let the user know they are passing in an unused arg

Use case

earth --build-arg ELIXIR=1.9.4 --build-arg OPT=20.3.8.26 +test
           buildkitd | Found buildkit daemon as docker container (earthly-buildkitd)
h/elixir:1.9.4-erlang-23.1.1-alpine-3.12.0 | --> Load metadata
h/elixir:1.9.4-erlang-23.1.1-alpine-3.12.0 | ERR