fix: Ensure footer test passes on big endian (#609)

This PR fixes the verification run failure for big endian, which is
currently failing on the `NanoarrowIpcNanoarrowFooterRoundtrip` tests.
Checked with:

```bash
export NANOARROW_ARCH=s390x
docker compose run --rm verify
```

---------

Co-authored-by: Benjamin Kietzman <bengilgit@gmail.com>

src/nanoarrow/ipc/decoder.c

@@ -1288,9 +1288,9 @@ ArrowErrorCode ArrowIpcDecoderDecodeFooter(struct ArrowIpcDecoder* decoder,
  struct ArrowIpcFileBlock* record_batches =
  (struct ArrowIpcFileBlock*)private_data->footer.record_batch_blocks.data;
  for (int64_t i = 0; i < n; i++) {
- record_batches[i].offset = blocks[i].offset;
- record_batches[i].metadata_length = blocks[i].metaDataLength;
- record_batches[i].body_length = blocks[i].bodyLength;
+ record_batches[i].offset = ns(Block_offset(blocks + i));
+ record_batches[i].metadata_length = ns(Block_metaDataLength(blocks + i));
+ record_batches[i].body_length = ns(Block_bodyLength(blocks + i));
  }
 
  decoder->footer = &private_data->footer;

src/nanoarrow/ipc/decoder_test.cc

@@ -984,7 +984,13 @@ TEST_P(ArrowSchemaParameterizedTestFixture, NanoarrowIpcNanoarrowFooterRoundtrip
  EXPECT_EQ(
  ArrowIpcEncoderFinalizeBuffer(encoder.get(), /*encapsulate=*/false, buffer.get()),
  NANOARROW_OK);
+
+#ifdef __BIG_ENDIAN__
+ uint32_t footer_size_le = bswap32(static_cast<uint32_t>(buffer->size_bytes));
+ EXPECT_EQ(ArrowBufferAppendInt32(buffer.get(), footer_size_le), NANOARROW_OK);
+#else
  EXPECT_EQ(ArrowBufferAppendInt32(buffer.get(), buffer->size_bytes), NANOARROW_OK);
+#endif
  EXPECT_EQ(ArrowBufferAppendStringView(buffer.get(), "ARROW1"_asv), NANOARROW_OK);
 
  struct ArrowBufferView buffer_view;
@@ -1005,6 +1011,7 @@ TEST_P(ArrowSchemaParameterizedTestFixture, NanoarrowIpcNanoarrowFooterRoundtrip
  struct ArrowIpcFileBlock roundtripped_block;
  memcpy(&roundtripped_block, decoder->footer->record_batch_blocks.data,
  sizeof(roundtripped_block));
+
  EXPECT_EQ(roundtripped_block.offset, dummy_block.offset);
  EXPECT_EQ(roundtripped_block.metadata_length, dummy_block.metadata_length);
  EXPECT_EQ(roundtripped_block.body_length, dummy_block.body_length);