Add rust lint CI job. (#9)

Additionally fix the many lint errors that are occurring. (or disable them).

Reviewed-on: #9
Co-authored-by: Drew Galbraith <drew@tiramisu.one>
Co-committed-by: Drew Galbraith <drew@tiramisu.one>

rust/lib/mammoth/src/cap_syscall.rs

@@ -2,7 +2,6 @@ use core::ffi::c_void;
 
 use crate::zion::{self, z_cap_t, ZError};
 
-#[must_use]
 fn syscall<T>(id: u64, req: &T) -> Result<(), ZError> {
     unsafe {
         let resp = zion::SysCall1(id, req as *const T as *const c_void);