build: fix compiler version detection

Compiler version tuples should be numeric for tuple comparisons
to work.

Also correct check for AIX where the minimum supported GCC is 6.3.0

PR-URL: https://github.com/nodejs/node/pull/24879


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>