clarify Builders

src/lib_json/json_reader.cpp

@@ -915,6 +915,8 @@ CharReaderBuilder::CharReaderBuilder()
   : collectComments_(true)
   , features_(Features::all())
 {}
+CharReaderBuilder::~CharReaderBuilder()
+{}
 CharReader* CharReaderBuilder::newCharReader() const
 {
   return new OldReader(collectComments_, features_);

src/lib_json/json_writer.cpp

@@ -971,6 +971,8 @@ StreamWriterBuilder::StreamWriterBuilder()
   : cs_(StreamWriter::CommentStyle::All)
   , indentation_("\t")
 {}
+StreamWriterBuilder::~StreamWriterBuilder()
+{}
 StreamWriter* StreamWriterBuilder::newStreamWriter(std::ostream* stream) const
 {
   std::string colonSymbol = " : ";