The su -c trick is telling the OS to run eggdrop as another user, this it is not a work around.
Simpler methods would be to learn how to add a user, login as that user, then follow the compile and comfigure steps. Them from then on, use this user to launch the eggdrop, and/or setup the crontab.
For those that don't read the warnings plastered over most linux software.
You should never run any peice of software as rot, unless you know exactly what the software does. Nor should you run a peice of software, if you do not trust the manufacturers.