test: check symbols in shared lib

When building the node with `--shared` option, we need
to verify the symbols in shared lib instead of executable.

Refs: https://github.com/nodejs/node/issues/18535



Signed-off-by: Yihong Wang <yh.wang@ibm.com>
PR-URL: https://github.com/nodejs/node/pull/18806
Refs: https://github.com/nodejs/node/issues/18535


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>