CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE

Added in version 3.8.

Visual Studio preferred tool architecture.

The Visual Studio Generators for VS 2013 and above support using either the 32-bit or 64-bit host toolchains by specifying a host=x86 or host=x64 value in the CMAKE_GENERATOR_TOOLSET option. CMake provides the selected toolchain architecture preference in this variable (x86, x64, ARM64 or empty).