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).
© 2000–2016 Kitware, Inc.
© 2000–2011 Insight Software Consortium
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.7/variable/XCODE_VERSION.html