Please check #5723 for this PR.

Hi thanks for the contribution. With this change, do the s2n-tls unit tests actually run and pass on AIX OS?

Yes, the s2n-tls unit tests passed on AIX OS. Below is the summary of the test case results.

281/282 Test #281: s2n_x509_validator_test ..........................   Passed    1.77 sec
        Start 282: s2n_x509_validator_time_verification_test
282/282 Test #282: s2n_x509_validator_time_verification_test ........   Passed    2.58 sec

100% tests passed, 0 tests failed out of 282

Label Time Summary:
unit    = 562.89 sec*proc (282 tests)

Total Test time (real) = 563.28 sec

I think it's fine if we accept this PR, unfortunately we can't run CI on AIX, so we can't guarantee that we won't break this usecase in the future. But since there's no real code changes that need to be made to support AIX, it's fine.
A note though, you should definitely keep running the s2n-tls unit tests on AIX. Minimally, those tests need to pass to say that s2n-tls is working properly in that environment. If one of them fails then it would not be safe to use s2n-tls on that OS.

Thank you for the review and for considering the PR.
Understood regarding the CI limitation on AIX. We will continue validating the changes on AIX locally to ensure that the build and functionality remain intact.