This is one of the big upsides of languages like C# or Java that have a lower-level virtual machine runtime that can be shared across different languages. In fact it was the suffering endured by the Gnome team trying to support different languages on top of C that eventually led to the Mono project.

Unfortunately there are also some downsides to the virtual machine approach but I still think there's a window of opportunity open here for Microsoft if they make the CLR robust and reliable on Mac and Linux.