VS: Provide the default platform name to project code
The value of
CMAKE_VS_PLATFORM_NAME is computed by Visual Studio
generators based on
CMAKE_GENERATOR_PLATFORM or some default.
Prior to the VS 2019 generator, the default was always
However, for the
Visual Studio 16 2019 generator, the default is
based on the host platform.
Store the default in a new
CMAKE_VS_PLATFORM_NAME_DEFAULT variable for
use by project code. This is particularly useful in toolchain files
because they are allowed to set
CMAKE_GENERATOR_PLATFORM and so
CMAKE_VS_PLATFORM_NAME is not yet known. Of course the toolchain file
author knows whether it will set
CMAKE_GENERATOR_PLATFORM, and if not
CMAKE_VS_PLATFORM_NAME_DEFAULT provides the platform name that
will be used.
Fixes: #19177 (closed)