XCODE_VERSION
Version of Xcode (Xcode generator only).
Under the Xcode generator, this is the version of Xcode as specified in Xcode.app/Contents/version.plist (such as 3.1.2).
© 2000–2019 Kitware, Inc. and Contributors
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.5/variable/XCODE_VERSION.html