yes, fl-shared is the path to the target library.
I would recommend you make sure to clean CMake derived files using the clean.sh file.
Also, I think you will have trouble building from source using -DFL_USE_FLOAT=ON. If you do, please use double precision instead by setting -DFL_USE_FLOAT=OFF or just not using the flag -DFL_USE_FLOAT (by default is OFF). I am working on some compiling issues I found using floats instead of double.