./configure --help
make

will try to re-run configure with --help
which isn't what was intended.

The reason is that config.status was written
even on configure error.
Defer writing config.status until configure
has completed successfully.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>