message: Add `__error` to freebsd shims
diff: @@ -24,6 +24,14 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  this.write_null(dest)?;
  }
  +
  + // errno
  + "__error" => {
  + let [] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  + let errno_place = this.last_error_place()?;
  + this.write_scalar(errno_place.to_ref(this).to_scalar()?, dest)?;
  + }
  +
  _ => return Ok(EmulateByNameResult::NotSupported),
  }
  Ok(EmulateByNameResult::NeedsJumping)
  