message: unify code paths
diff: @@ -154,14 +154,11 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a + 'mir>: crate::MiriEvalContextExt<'
  "__rust_start_panic" | "panic_impl" => {
  return err!(MachineError("the evaluated program panicked".to_string()));
  }
  - "exit" => {
  + "exit" | "ExitProcess" => {
  + // it's really u32 for ExitProcess, but we have to put it into the `Exit` error variant anyway
  let code = this.read_scalar(args[0])?.to_i32()?;
  return err!(Exit(code));
  }
  - "ExitProcess" => {
  - let code = this.read_scalar(args[0])?.to_u32()?;
  - return err!(Exit(code as i32));
  - }
  _ => if dest.is_none() {
  return err!(Unimplemented(
  format!("can't call diverging foreign function: {}", link_name),
  