Runner: Validate support for macOS hosts

Support requested in one of the questions of #76 (closed) by @alexifm.

Issues and tasks identified:

• README: Add macOS references
• TEST: Add macOS references
• const: Add IS_MAC_OS evaluation
• runner: Validate support of --real-paths or disallow
• runner: Validate support of native scripts
• utils: Validate support of path resolutions and volumes mounts
• engine: Validate support for sockets mounts (with --sockets and EXPERIMENTAL=true)
• settings: Adapt for ~/Library/Preferences