Okay, so from this it appears that fbclient 3.x has basically no required external dependencies? I'm not sure how tommath relates to threading and atomics, it appears to be a MPI library. Conan just relies on pthread for threading on *nix systems.
Conan packages zlib, so an option for that is no problem. Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
