include doublequote characters in string literal token text

src/parser/parser.l

@@ -150,12 +150,13 @@ L?\" {
     {
         delete build_string;
     }
-    build_string = new std::string();
+    build_string = new std::string("\"");
     BEGIN(str);
 }
 <str>{
 \" {
     BEGIN(INITIAL);
+    *build_string += "\"";
     (*yylval)->token.text = build_string;
     build_string = nullptr;
     return STRING_LITERAL;