Rechi authored Sep 25, 2020 and Brad King committed Sep 25, 2020

Generate the same default `CMAKE_INSTALL_PREFIX` if a project is
configured with CMAKE_GENERATOR_PLATFORM (`cmake -G "Visual Studio
[...]" -A x64` and `cmake -G "Visual Studio [...]" -A ARM`) instead of
the prior CMake 3.1 way (`cmake -G "Visual Studio [...] Win64"` and
`cmake -G "Visual Studio [...] ARM"`).