CDRIVER-6103 AIX build failure fix

[shubhamhii]

This PR fixes the signbit symbol missing issue.

Below is the issue URL.

https://jira.mongodb.org/browse/CDRIVER-6103

[rcsanchez97]

Can you confirm that the Boolean logic is correct? It looks to me like it should rather be && !defined(_AIX), otherwise the logic breaks. For example the way you have implemented the check, if __FreeBSD__ were defined and _AIX were not defined(i.e., because we are compiling on FreeBSD) then the condition would be false && (true || false) || true. This evaluates to an overall value of true, and results in the call to signbit on a platform that doesn't have it (FreeBSD in this case).

[shubhamhii]

Can you confirm that the Boolean logic is correct? It looks to me like it should rather be && !defined(_AIX), otherwise the logic breaks. For example the way you have implemented the check, if __FreeBSD__ were defined and _AIX were not defined(i.e., because we are compiling on FreeBSD) then the condition would be false && (true || false) || true. This evaluates to an overall value of true, and results in the call to signbit on a platform that doesn't have it (FreeBSD in this case).

Thanks for pointing it out.
Corrected the logic.

[kevinAlbs]

Thank you for the contribution @shubhamhii!

[shubhamhii]

Thank you for the contribution @shubhamhii!

Thanks a lot for your help.