VS: Fix x64 host recognition by x86 cmake process
In !2789 (merged) and !2870 (merged) we intended to select the
x64 target architecture and
x64 host tools by default on x64 host machines. Fix detection of a x64 host when CMake itself is a 32-bit x86 process.
The KWSys SystemInformation
Is64Bits member is not set correctly, which led to this bug. Pending investigation on the KWSys side, simply test ourselves via