Remove special case for Linux in addRunDestinationSettingsPlatformSDK

[jakepetroules]

This function does some Linux-specific checks (see destinationPlatformIsLinux) in settings construction in relation to the run destination. This stems from some earlier Linux support work for which the specific reasons have been lost to time.

We should remove this to avoid odd subtle differences between Linux and other/future platforms such as Android, FreeBSD, and so on.

[jakepetroules]

Not sure why macOS is special-cased either, as compared to iOS, tvOS, etc.