Linux Swift 2

You can't as it doesn't exist yet. Comming in fall was the wording in the keynote yesterday.

The official announcement states that they are releasing Swift 2 compiler with the standard library :

https://developer.apple.com/swift/blog/?id=29

https://developer.apple.com/library/prerelease/ios/documentation/General/Reference/SwiftStandardLibraryReference/index.html

So, I am assumming/hoping that only targeting the standard library will mean that it will compile on Linux when available.