Target specific architectures for macOS and iOS.
This variable is used to initialize the
property on each target as it is created. See that target property
for additional information.
The value of this variable should be set prior to the first
enable_language() command invocation
because it may influence configuration of the toolchain and flags.
It is intended to be set locally by the user creating a build tree.
This variable should be set as a
CACHE entry (or else CMake may
remove it while initializing a cache entry of the same name).
OSX part in the variable name(s) they apply also to
other SDKs than macOS like iOS, tvOS, or watchOS.
This variable is ignored on platforms other than Apple.