message: Prevent different vtables with the same name
  Fixes
diff: @@ -136,12 +136,13 @@ fn build_vtable<'tcx>(
  .module
  .declare_data(
  &format!(
  - "__vtable.{}.for.{:?}",
  + "__vtable.{}.for.{:?}.{}",
  trait_ref
  .as_ref()
  .map(|trait_ref| format!("{:?}", trait_ref.skip_binder()).into())
  .unwrap_or(std::borrow::Cow::Borrowed("???")),
  - layout.ty
  + layout.ty,
  + fx.vtables.len(),
  ),
  Linkage::Local,
  false,
  @@ -158,10 +159,7 @@ fn build_vtable<'tcx>(
  )
  .unwrap();
  - match fx.module.define_data(data_id, &data_ctx) {
  - Ok(()) | Err(cranelift_module::ModuleError::DuplicateDefinition(_)) => {}
  - err => err.unwrap(),
  - }
  + fx.module.define_data(data_id, &data_ctx).unwrap();
  data_id
  }
  