add ability to run `glint --build` specifying a `--project` like tsc

[hmajoros]

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tsc allows you to run tsc --build custom-tsconfig.json, to essentially use the --project flag & tsc --build flag simultaneously.

should glint --build also support this functionality? I am assuming yes after speaking with @chriskrycho, but I understand the yargs story with defaults is... complicated

[chriskrycho]

It would definitely be convenient, but/and yargs does not supply a good interface for it.