Automatically build the best available platform in Visual C ++ (equivalent to gcc -march = native)

I would like to distribute the Visual Studio project files as part of the source only distribution so that it automatically builds its own custom machine architecture. So if they have 64 bits they will be built for it, if they have AVX or AVX2 they will be built for them. This is what gcc -march = own flag does. I haven't been able to find an equivalent to this with visual studio - does one exist or is there a workaround? I am using Visual Studio Express 2013 and I would like this to be something that could work with one of the free versions of Express as most users will not have access to one of the paid versions. Thank!