doc: fix/add link to Android info

We have two notes in API docs about Android support:
the first has no links, the second links to the table of supported OSs
where Android is not mentioned which may be confusing.

This PR makes both notes link to dedicated Android part of BUILDING.md.

PR-URL: https://github.com/nodejs/node/pull/19004


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>