Add information gathered through getauxval()

Summary:
Partial backport of core PR17270:
https://github.com/bitcoin/bitcoin/pull/17270/commits/483b94292e89587e5ab40a30b8a90e2f56e847f3

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6206