CMake/Help/variable/CMAKE_POLICY_DEFAULT_CMPNNNN.rst

CMAKE_POLICY_DEFAULT_CMP<NNNN>
------------------------------

Default for CMake Policy CMP<NNNN> when it is otherwise left unset.

Commands cmake_minimum_required(VERSION) and cmake_policy(VERSION) by
default leave policies introduced after the given version unset.  Set
CMAKE_POLICY_DEFAULT_CMP<NNNN> to OLD or NEW to specify the default
for policy CMP<NNNN>, where <NNNN> is the policy number.

This variable should not be set by a project in CMake code; use
cmake_policy(SET) instead.  Users running CMake may set this variable
in the cache (e.g.  -DCMAKE_POLICY_DEFAULT_CMP<NNNN>=<OLD|NEW>) to set
a policy not otherwise set by the project.  Set to OLD to quiet a
policy warning while using old behavior or to NEW to try building the
project with new behavior.