Fix hardened build check
    
    CheckDaemonCompileFlags checked that '%global _hardened_build' appears
    when certain vulnerable conditions were met.
    For a long time already, the hardened build is the default.
    Correspondingly, the packaging guidelines have changed
    so that disabling hardened build is forbidden in certain conditions.
    Updated the check to look for '%undefine _hardened_build' instead
    and pass or fail the test accordingly.
    
    Resolves #436