[CMake] Add configuration support to include_directories()

[Bill Hoffman]

>     Investigate CMAKE_CFG_INTDIR.
> 
> 
> I believe for Visual Studio output, this will be $(OutDir), right? If 
> this is the case, this is a visual studio environment variable that will 
> have no meaning when used in CMake scripts.
> 

It is . when not in VS, and $(OutDir) when it is.  So, you can say 
/foo/bar/bin/${CMAKE_CFG_INTDIR}/runit.

It will be /foo/bar/bin/./runit with makefiles.
It will be /foo/bar/bin/$(OutDir)/runit with VS projects.

-Bill