New in version 3.19.2.

On Apple Silicon hosts running macOS, set this variable to tell CMake what architecture to use for CMAKE_HOST_SYSTEM_PROCESSOR. The value must be either arm64 or x86_64.

The value of this variable should never be modified by project code. It is meant to be set as a cache entry provided by the user, e.g. via -DCMAKE_APPLE_SILICON_PROCESSOR=....

See also the CMAKE_APPLE_SILICON_PROCESSOR environment variable.