s390: enable march=z196

PR-URL: https://github.com/nodejs/node/pull/11730


Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>