main/nagios-plugins: fix compilation with wrong mysql-import
This fixes the current build errors on 3.13 builders (like https://build.alpinelinux.org/buildlogs/build-3-13-armv7/main/nagios-plugins/nagios-plugins-2.3.2-r0.log)
We are currently working on getting Alpine Linux 3.21 out. This means that merge requests that are not aimed to help with that (only affecting testing, new aports) have a lower priority at the moment. Please be patient, they will be eventually picked up.
This fixes the current build errors on 3.13 builders (like https://build.alpinelinux.org/buildlogs/build-3-13-armv7/main/nagios-plugins/nagios-plugins-2.3.2-r0.log)