The Nim programming language compiles (optionally) to plain C. What other languages do that? Vala does, but it depends on GLib and GObject. What else?
Why? Because the Turaco SDK compiles C99 -- so, in theory, any language that compiles to C99 should be possible to use with it.
Oh, look, a big list of them: https://github.com/dbohdan/compilers-targeting-c