I usually advise against installing ARGoS from the sources – do you have a specific reason why you did it by hand instead of using the precompiled packages?
That error can be solved with the following steps:
- Make sure that you performed sudo make install
- Make sure that the folder /usr/local/lib/argos3 is not empty
- Make sure the file /etc/ld.so.conf.d/argos3.conf exists and it contains /usr/local/lib/argos3
- Run sudo ldconfig, which will make sure your linker looks into /usr/local/lib/argos3 (provided the check at 3. succeeds)
I made ARGoS.