For dependencies that on some systems are built into libc etc. and don't
need to be separately linked. This is distinct from "system"
dependencies which add linker args.
This allow mypy to catch cases where we accidently assign the dependency
name to the type_name, as it sees them as having different types (though
at runtime they're all strings).
Christian Clauss
Eli Schwartz
Dylan Baker
Daniel Mensinger