Build: fix error message for missing C libraries
Build: fix error message for missing C libraries

Closes #271.

[skip ci]

c-cube/lwt,rneswold/lwt,ocsigen/lwt,rgrinberg/lwt,ocsigen/lwt,rgrinberg/lwt,rgrinberg/lwt,rneswold/lwt,c-cube/lwt,c-cube/lwt,ocsigen/lwt,rneswold/lwt,rgrinberg/lwt