fix test failure in arrow test

Author: gty404

src/iceberg/table_metadata.cc

@@ -933,7 +933,9 @@ TableMetadataBuilder& TableMetadataBuilder::SetCurrentSchema(int32_t schema_id)
 TableMetadataBuilder& TableMetadataBuilder::AddSchema(
     std::shared_ptr<Schema> const& schema) {
   ICEBERG_BUILDER_ASSIGN_OR_RETURN(auto highest_field_id, schema->HighestFieldId());
-  impl_->AddSchema(*schema, std::max(impl_->metadata().last_column_id, highest_field_id));
+  auto new_last_column_id = std::max(impl_->metadata().last_column_id, highest_field_id);
+  ICEBERG_BUILDER_ASSIGN_OR_RETURN(auto schema_id,
+                                   impl_->AddSchema(*schema, new_last_column_id));
   return *this;
 }
 

src/iceberg/test/metadata_io_test.cc

@@ -33,6 +33,7 @@
 #include "iceberg/result.h"
 #include "iceberg/schema.h"
 #include "iceberg/snapshot.h"
+#include "iceberg/sort_order.h"
 #include "iceberg/table_metadata.h"
 #include "iceberg/table_properties.h"
 #include "iceberg/test/matchers.h"
@@ -75,6 +76,7 @@ class MetadataIOTest : public TempFileTestBase {
                              .manifest_list = "s3://a/b/1.avro",
                              .summary = {{"operation", "append"}},
                          })},
+                         .sort_orders = {SortOrder::Unsorted()},
                          .default_sort_order_id = 0,
                          .next_row_id = 0};
   }