[CMake] Properly Detecting Win64

[Bill Hoffman]

On 4/12/2011 4:13 PM, David Cole wrote:

> Does somebody have reproducible steps to get to the point where
> CMAKE_SIZEOF_VOID_P disappears??
>
> I've never seen that...
>
> How many times do you have to re-configure before you start seeing this
> behavior? That sounds like something is just really wrong somewhere, and
> it would be a good thing to track down exactly what that is.
>
This variable is stored in this file:

CMakeFiles/CMakeCCompiler.cmake

It should not go away.

-Bill