remote: always build generated source files
    
    The generated source files for dispatching libvirtd RPC messages contain
    translations and are thus listed in POTFILES. This means they are
    required in order to build libvirt.pot. Rather than changing the files
    that go into libvirt.pot dynamically, just unconditionally build the
    remote driver sources so they are always available for building
    libvirt.pot. This ensures we don't silently loose translation messages
    based on configure args.
    
    This fixes the mingw build which needs to create libvirt.pot but has
    libvirtd disabled.
    
    Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>