[CMake] CMake, Visual Studio and cross-compilation.

[Max Savenkov]

Lately, there appeared some tools that allow C++ programmers to use 
Visual Studio for cross-compiling code for platforms other than Windows. 
I would very much like to generate projects that use these tools with CMake.

There are two cases I'm primarily interested in:
vs-android (and NVidia's VS addon that is based on it), which allows 
cross-compilation to Android
vs-tool (https://github.com/juj/vs-tool), which allows cross-compilation 
into JavaScript using Emscripten

Both work by adding a new Platform type to use in Visual Studio.

As far as I understand, there is no way to generate Visual Studio 
solutions that support these new platforms presently (if there is one, 
please tell me).
Depending on complexity of task, I'm maybe ready to get my hands dirty, 
but first I need some advice. Where should I start? Is there some kind 
of a guide about adding a new platform (it would be a new generator, 
wouldn't it?) to CMake?