[CMake] environment variables and visual studio

[Jesper Eskilson]

Is there any way for CMake to set environment variables which can be
picked up in Visual Studio's pre/post-build steps?

I'm working on a system where I've got a couple of studio project
included via the INCLUDE_EXTERNAL_MSPROJECT(), and I would like to be
able to refer to things like CMAKE_BINARY_DIR, so that the external
msprojects can put their output relative to the CMake build dir.

-- 
/Jesper