Currently, `arc lint` will construct the `ArcanistLintEngine` (and add all `ArcanistLinter` instances) before actually performing the linting. An unfortunate result of this is that the user will require all external linters to be installed, even if they have not modified any files which requires those linters.
For example, suppose that a user modifies `README.txt` and executes `arc diff`. Suppose that the repository is configured to lint `*.json` files with `ArcanistJSONLintLinter` (which requires the external `jsonlint` binary to be installed). In this case, `arc diff` will fail if the user does not have `ArcanistJSONLintLinter` installed, even though it should not technically be required.