[CMake] Generate Xcode projects on a Windows environment

[Hertout Julien]

We need to generate Xcode projects but from a Windows environment. CMake 
does the job well on a MAC OS environment. However, it can't do it on a 
Windows environment. I wonder if there are some technical reasons to it 
or if it is just a choice made by the CMake development team since this 
use case is outside the scope of CMake use.

I quickly looked at the source code of CMake and saw that, for the "Mac" 
version, the version.plist file of Xcode is read to know the installed 
version. Then, this is used to generate the good version of the project. 
Is it the only technical reason why Xcode projects must be generated on 
a Mac ?

Thanks.

J Hertout