message: Make saved_file field of WorkProduct non-optional
  A WorkProduct without a saved file is useless
diff: @@ -80,13 +80,9 @@ fn reuse_workproduct_for_cgu(
  cgu: &CodegenUnit<'_>,
  work_products: &mut FxHashMap<WorkProductId, WorkProduct>,
  ) -> CompiledModule {
  - let mut object = None;
  let work_product = cgu.previous_work_product(tcx);
  - if let Some(saved_file) = &work_product.saved_file {
  - let obj_out =
  - tcx.output_filenames(()).temp_path(OutputType::Object, Some(cgu.name().as_str()));
  - object = Some(obj_out.clone());
  - let source_file = rustc_incremental::in_incr_comp_dir_sess(&tcx.sess, &saved_file);
  + let obj_out = tcx.output_filenames(()).temp_path(OutputType::Object, Some(cgu.name().as_str()));
  + let source_file = rustc_incremental::in_incr_comp_dir_sess(&tcx.sess, &work_product.saved_file);
  if let Err(err) = rustc_fs_util::link_or_copy(&source_file, &obj_out) {
  tcx.sess.err(&format!(
  "unable to copy {} to {}: {}",
  @@ -95,14 +91,13 @@ fn reuse_workproduct_for_cgu(
  err
  ));
  }
  - }
  work_products.insert(cgu.work_product_id(), work_product);
  CompiledModule {
  name: cgu.name().to_string(),
  kind: ModuleKind::Regular,
  - object,
  + object: Some(obj_out),
  dwarf_object: None,
  bytecode: None,
  }
  