build: set `-blibpath:` for AIX

https://github.com/nodejs/node/pull/17604 refactored the gyp files
so that `-blibpath:` on AIX was only set if `node_shared=="true"`.
Restore the setting for non-shared builds.

Fixes: https://github.com/nodejs/node/issues/25444

Backport-PR-URL: https://github.com/nodejs/node/pull/26478
PR-URL: https://github.com/nodejs/node/pull/25447


Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>