Serialization: record OPAQUE_RETURN_TYPE_DECLS for llvm readers

Author: xymus

lib/Serialization/Serialization.cpp

@@ -904,6 +904,7 @@ void Serializer::writeBlockInfoBlock() {
   BLOCK_RECORD(index_block, SUBSTITUTION_MAP_OFFSETS);
   BLOCK_RECORD(index_block, CLANG_TYPE_OFFSETS);
   BLOCK_RECORD(index_block, LOCAL_TYPE_DECLS);
+  BLOCK_RECORD(index_block, OPAQUE_RETURN_TYPE_DECLS);
   BLOCK_RECORD(index_block, PROTOCOL_CONFORMANCE_OFFSETS);
   BLOCK_RECORD(index_block, PACK_CONFORMANCE_OFFSETS);
   BLOCK_RECORD(index_block, SIL_LAYOUT_OFFSETS);