Build error with glibc >= 2.32

## Problem description
Ubuntu 22.04+ ships with glibc 2.32 or newer. From the release notes at https://sourceware.org/pipermail/libc-announce/2020/000029.html:

> The deprecated arrays sys_siglist, _sys_siglist, and sys_sigabbrev are no longer available to newly linked binaries, and their declarations have been removed from . They are exported solely as compatibility symbols to support old binaries. All programs should use strsignal instead.

https://github.com/aws/amazon-redshift-odbc-driver/blob/main/src/pgclient/src/port/exec.c#L529

Changing that line to `strsignal` call corrects the build error. This probably needs to be wrapped in a different macro conditional based on glibc version.

Start at src/pgclient/src/port/exec.c around line 529 and inspect the existing macro conditions around the deprecated signal-list reference. Build the driver on Ubuntu 22.04 or newer to reproduce the glibc error, then verify the updated conditional behavior and successful build using strsignal as indicated by the issue.

Written by the indexing model from the issue text.