perf(cli): only check system on commands

[erickzhao]

Instead of running the system check on every electron-forge CLI run, this PR instead skips it by default if no command is run or if the --help option is triggered on a command.

This is inspired by @CodeWitchBella's comment in #3313, which I'm reading almost 2 years late (sorry 🙇).

Sidenote: I'd argue that this check should not run at all for things like --version or --help to make debugging a bit less painful. Also, the message references git and node.js when the issue is with yarn version.

[BlackHole1]

LGTM