48bdd4811e
`MacOS.sdk` and `.sdk_path` will now return the newest installed SDK instead of nil if called on a system that doesn’t have an SDK for the currently-installed OS. For example, Xcode 7 on OS X 10.10 does not include the 10.10 SDK, only the 10.11 SDK; software can be built by specifying both SDKROOT and MACOSX_DEPLOYMENT_TARGET.