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 Win32
.
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
then CMAKE_VS_PLATFORM_NAME_DEFAULT
provides the platform name that
will be used.
Fixes: #19177 (closed)