Updates ENG-2848
We can safely disable the App Sandbox for our macsys GUI, allowing us to use `tailscale ssh` and do a few other things that we've wanted to do for a while. This PR:
- allows Tailscale SSH to be used from the macsys GUI binary when called from a CLI
- tweaks the detection of client variants in prop.go, with new functions `IsMacSys()`, `IsMacSysApp()` and `IsMacAppSandboxEnabled()`
Signed-off-by: Andrea Gottardo <andrea@gottardo.me>
returnerrors.New("The 'tailscale ssh' subcommand is not available on sandboxed macOS builds.\nUse the regular 'ssh' client instead.")
returnerrors.New("The 'tailscale ssh' subcommand is not available on macOS builds distributed through the App Store or TestFlight.\nInstall the Standalone variant of Tailscale (download it from https://pkgs.tailscale.com), or use the regular 'ssh' client instead.")