New in version 3.12.

If CMAKE_SUPPRESS_REGENERATION is OFF, which is default, then CMake adds a special target on which all other targets depend that checks the build system and optionally re-runs CMake to regenerate the build system when the target specification source changes.

If this variable evaluates to ON at the end of the top-level CMakeLists.txt file, CMake will not add the regeneration target to the build system or perform any build system checks.