The Zither Rust syscall backend is responsible for generating thin FFI syscall wrappers, derived from the FIDL syscall specifications of library zx.
A crate of name fuchsia-zircon-sys is generated, but has no particularly documented layout.
${fidl_target}_zither.rust_syscall generates a rustc_library() target defining the crate.
Any declaration type not mentioned below is ignored.
Each syscall declaration yields one FFI wrapper in the crate.