CMAKE_Swift_LANGUAGE_VERSION

New in version 3.7.

Set to the Swift language version number. If not set, the oldest legacy version known to be available in the host Xcode version is assumed:

Swift 4.0 for Xcode 10.2 and above.
Swift 3.0 for Xcode 8.3 and above.
Swift 2.3 for Xcode 8.2 and below.

© 2000–2022 Kitware, Inc. and Contributors
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.23/variable/CMAKE_Swift_LANGUAGE_VERSION.html