config generator (including setting MIBDIRS) when changing the generator input file. add an example showing use with OPENBSD-PF-MIB (which just had a commit in src/ that will prevent snmp_exporter from using a hexdump of various names, so if someone is trying this right now they should pick up the updated MIB first). Parts borrowed from https://yetiops.net/posts/openbsd-snmp-exporter/