Fix BANN build failure after adding streamingDiskANN. (#257)

* Fix BANN build failure after adding streamingDiskANN.

* Throw exception when calling load_pq_centroid_bin if EXEC_ENV_OLS is defined.

* Fix Variable name.

* Remove commented line.

Author: NingyuanChen

src/index.cpp

@@ -1424,7 +1424,12 @@ namespace diskann {
       copy_aligned_data_from_file<_u8>(pq_compressed_file.c_str(), _pq_data,
                                        file_num_points, _num_pq_chunks,
                                        _num_pq_chunks);
+#ifdef EXEC_ENV_OLS
+      throw ANNException("load_pq_centroid_bin should not be called when EXEC_ENV_OLS is defined.",
+                         -1, __FUNCSIG__, __FILE__, __LINE__);
+#else
       _pq_table.load_pq_centroid_bin(pq_pivots_file.c_str(), _num_pq_chunks);
+#endif
     }
 
     copy_aligned_data_from_file<T>(filename, _data, file_num_points, file_dim,