message: implement aarch64 hint 'intrinsic'
diff: @@ -484,6 +484,18 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  let &[] = check_arg_count(args)?;
  this.yield_active_thread();
  }
  + "llvm.aarch64.hint" if this.tcx.sess.target.arch == "aarch64" => {
  + let &[hint] = check_arg_count(args)?;
  + let hint = this.read_scalar(hint)?.to_i32()?;
  + match hint {
  + 1 => { // HINT_YIELD
  + this.yield_active_thread();
  + }
  + _ => {
  + throw_unsup_format!("unsupported llvm.aarch64.hint argument {}", hint);
  + }
  + }
  + }
  // Platform-specific shims
  _ => match this.tcx.sess.target.os.as_str() {
  