Do not preserve ownership or xattrs on copied files
    
    As noticed in https://bugzilla.redhat.com/show_bug.cgi?id=2239008#c16, when
    compiling a kernel as a user and doing 'sudo make install', and when using a
    non-vfat fs for the install destination, the file would end up owned by the
    user. This is not useful at all, so let's only preserve the timestamps on the
    copied file, no other attributes.
    
    Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>