Fix cmake warning

[ellert]

See: cmake --help-policy CMP0022

[mpatrascoiu]

Thanks!

According to the cmake --help-policy manual:

This policy was introduced in CMake version 2.8.12.  CMake version
2.8.12.2 warns when the policy is not set and uses OLD behavior.  Use
the cmake_policy command to set it to OLD or NEW explicitly.

This tells me OLD is used by default, which ignores the new INTERFACE_LINK_LIBRARIES syntax.
I wanted to make sure this change will be intentional and not have consequences, which looks like it won't until the moment we use cmake_policy(NEW).