Compiler version string.
Compiler version in major[.minor[.patch[.tweak]]] format. This variable is not guaranteed to be defined for all compilers or languages.
© 2000–2016 Kitware, Inc.
© 2000–2011 Insight Software Consortium
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.7/variable/CMAKE_LANG_COMPILER_VERSION.html