I compiled the kext using xcode 6.2 in Mavericks. I had a one compilation error that I solved quickly. The only doubt I have is, how can I have the Release version instead of the Debug one.
From the "Products" menu select "Archive". After that, select the built driver archive in the Organizer window which appears and click "Export" to save the release build somewhere, e.g. on the Desktop. In this folder you'll find a directory hierarchy with the release version of the driver in it.