if() IN_LIST operator.
CMake 3.3 adds support for the new IN_LIST operator.
OLD behavior for this policy is to ignore the IN_LIST operator.
NEW behavior is to interpret the IN_LIST operator.
This policy was introduced in CMake version 3.3.
CMake version 3.6.2 warns when the policy is not set and uses
OLD behavior. Use the
cmake_policy() command to set
OLD behavior of a policy is
deprecated by definition
and may be removed in a future version of CMake.