message: clean up destructuring assignment
  Removes a fixme
diff: @@ -428,17 +428,13 @@ pub fn create_bcx<'a, 'cfg>(
  // Rebuild the unit graph, replacing the explicit host targets with
  // CompileKind::Host, removing `artifact_target_for_features` and merging any dependencies
  // shared with build and artifact dependencies.
  - let new_graph = rebuild_unit_graph_shared(
  + (units, scrape_units, unit_graph) = rebuild_unit_graph_shared(
  interner,
  unit_graph,
  &units,
  &scrape_units,
  host_kind_requested.then_some(explicit_host_kind),
  );
  - // This would be nicer with destructuring assignment.
  - units = new_graph.0;
  - scrape_units = new_graph.1;
  - unit_graph = new_graph.2;
  }
  let mut extra_compiler_args = HashMap::new();
  