Fix JNI build broken by to_arrow signature change (#6595)

#6430 added struct_type support to to_arrow()/from_arrow().
The change in signature broke cudf/jni code.
This commit fixes that break.

CHANGELOG.md

@@ -38,6 +38,7 @@
 - PR #6543 Handle `np.nan` values in `isna`/`isnull`/`notna`/`notnull`
 - PR #6549 Fix memory_usage calls for list columns
 - PR #6575 Fix JNI RMM initialize with no pool allocator limit
+- PR #6595 Fix JNI build, broken by to_arrow() signature change
 
 
 # cuDF 0.16.0 (21 Oct 2020)

java/src/main/native/src/TableJni.cpp

@@ -1190,7 +1190,15 @@ JNIEXPORT jlong JNICALL Java_ai_rapids_cudf_Table_convertCudfToArrowTable(JNIEnv
   try {
     cudf::jni::auto_set_device(env);
     std::unique_ptr<std::shared_ptr<arrow::Table>> result(new std::shared_ptr<arrow::Table>(nullptr));
-    *result = cudf::to_arrow(*tview, state->column_names);
+    auto column_metadata = std::vector<cudf::column_metadata>{};
+    column_metadata.reserve(state->column_names.size());
+    std::transform(
+      std::begin(state->column_names),
+      std::end(state->column_names),
+      std::back_inserter(column_metadata),
+      [](auto const& column_name) { return cudf::column_metadata{column_name}; }
+    );
+    *result = cudf::to_arrow(*tview, column_metadata);
     if (!result->get()) {
       return 0;
     }