When the arc linters workflow was added, it added a dependency on this method being public. If you create a new lint engine with the scope set to protected (as in the parent) and specify that linter in your .arcconfig file, arc linters would fatal error out with a message like:
Fatal error: Call to protected method Firehed\Arctools\LintEngine::buildLinters() from context 'ArcanistLintersWorkflow' in /Users/firehed/dev/arcanist/src/workflow/ArcanistLintersWorkflow.php on line 44
Call Stack:
0.0007 332136 1. {main}() /Users/firehed/dev/arcanist/scripts/arcanist.php:0
0.0354 6939256 2. ArcanistLintersWorkflow->run() /Users/firehed/dev/arcanist/scripts/arcanist.php:338