Add INSTALL_BROKEN_KAUTH_POLICY_FILES cmake option

It allows installing the policy files into CMAKE_INSTALL_PREFIX instead of to kauth prefix. If those two prefixes are different, this is BAD and will not work, but in some cases (e.g. i'm compiling all of KDE Gear and just want to make sure things compile) I don't care, so having an option to say "I know this is broken, but just continue" is super welcome.