message: Add __errno_location shim
diff: @@ -418,6 +418,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  }
  }
  + "__errno_location" => {
  + let errno_scalar: Scalar<Tag> = this.machine.last_error.unwrap().into();
  + this.write_scalar(errno_scalar, dest)?;
  + }
  +
  "getenv" => {
  let result = this.getenv(args[0])?;
  this.write_scalar(result, dest)?;
  