New in version 3.9.
Read-only property that is true on multi-configuration generators.
True when using a multi-configuration generator (such as Visual Studio Generators or Xcode). Multi-config generators use CMAKE_CONFIGURATION_TYPES as the set of configurations and ignore CMAKE_BUILD_TYPE.
© 2000–2020 Kitware, Inc. and Contributors
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.19/prop_gbl/GENERATOR_IS_MULTI_CONFIG.html