Set CMake policy version lower bound to 3.5

[penguinpee]

Also specify upper bound as 4.0.

With CMake 4.0 policies before 3.5 will be dropped. CMake 4.0 also requires the upper bound to be specified.

[penguinpee]

Fedora is planning to upgrade CMake to 4.0.

I tested the Linux build with CMake 4.0 as well as CMake 3.30.8 and didn't notice any regression. I did not test the Android build nor any of the third party libraries (we do not use them). I just assumed they would be compatible.

More info:

https://cmake.org/cmake/help/latest/release/4.0.html https://cmake.org/cmake/help/latest/manual/cmake-policies.7.html#unsupported-policies