fix: allow absolute --path/--dir for typechecking

[danielbayley]

Currently, any --path/--dir given to brew typecheck is forcibly prefixed with ../, which breaks this functionality under most circumstances. This PR enables passing an absolute --path, or --dir to typecheck, with the goal being that we can make use of it with 3rd party taps…

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[MikeMcQuaid]

Hey, thanks! One comment.

[MikeMcQuaid]

Thanks!