New in version 3.19.
Xcode build system selection.
Xcode generator defines this variable to indicate which
variant of the Xcode build system will be used. The value is the
version of Xcode in which the corresponding build system first became
mature enough for use by CMake. The possible values are:
The original Xcode build system. This is the default when using Xcode 11.x or below.
The Xcode "new build system" introduced by Xcode 10. It became mature enough for use by CMake in Xcode 12. This is the default when using Xcode 12.x or above.
CMAKE_XCODE_BUILD_SYSTEM variable is informational and should not
be modified by project code. See the Toolset and Build System Selection
documentation section to select the Xcode build system.