WinRT app deployment to multiple devices

If you build 开发者_C百科app against WinRT, can you deploy it to any device or do you have to have multiple builds (one per platform) like you do right now?

WinRT applications built in JavaScript or C# will deploy without changes to any Win8 machine. This includes Arm devices per Steven Sinofsky's keynote. Applications written in C++ will need to be compiled for the appropriate architecture (x86, x64, Arm), but should not require any source modifications.