New Issue Checklist

• I've Updated SwiftLint to the latest version.
• I've searched for existing GitHub issues.

Feature or Enhancement Proposal

Currently, SwiftLintBuildToolPlugin outputs a log on every invocation for every target of the format:

Environment: ["BUILD_WORKSPACE_DIRECTORY": "/Users/tonyarnold/Developer/Mantel/Reveal/Packages/RevealSupport"]

This really doesn't provide any detail that's helpful or actionable to people who aren't developing SwiftLint, so I was hoping that there might be a way to disable it (or perhaps only show the logging in DEBUG builds?).