I'm inclined to drop the symbols file altogether, as it really doesn't add any value. The correct solution would be to use -fvisibility=hidden [1] and properly tag symbols for the public API of libArcus and libSavitar.
For what it's worth, libArcus.so.3 is currently only used by python3-arcus and CuraEngine anyway, and it's unlikely that this will change. Another option would be to put all the internal Cura libraries into a private lib folder, but I suspect this is risky and even more work than adding symbol visibility. [1] http://gcc.gnu.org/wiki/Visibility
