This version includes an important bugfix to avoid including unnecessary
-Wl,-rpath flags.  It also avoids the warnings on custom_targets with
more than one output.

Reported-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Tested-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>