To list available Liberation fonts:

fc-list | Liberation

/usr/share/fonts/TTF/LiberationMono-Regular.ttf: Liberation Mono:style=Regular

vim config.h

static char *font = "Liberation Mono:style=Regular:pixelsize=16:antialias=true:autohint=true";

So, you list the fonts, then copy the font name and style part and add that to the front of :pixelsize etc in config.h