For each toolset that comes with this version of Visual Studio, there are
variants that are themselves compiled for 32-bit (x86) and 64-bit (x64) hosts
(independent of the architecture they target).
|VS_TOOLSET_HOST_ARCH_DEFAULT|
One may explicitly request use of either the 32-bit or 64-bit host tools
by adding either ``host=x86`` or ``host=x64`` to the toolset specification.
See the :variable:`CMAKE_GENERATOR_TOOLSET` variable for details.