The radius client library can be selected by setting either `FREERADIUS` or `USE_RADCLI` to 1 when compiling radius modules, see `Makefile.radius`:
* https://github.com/kamailio/kamailio/blob/master/src/Makefile.radius
Like:
``` make FREERADIUS=1 modules modules=src/modules/auth_radius ```
Should anyone have a way/ideas to improve this (either in Makefile or via docs), a pull request will be appreciated.