MDEV-23766: Re-add Json_writer unit test.

unittest/sql/CMakeLists.txt

@@ -37,3 +37,7 @@ TARGET_LINK_LIBRARIES(mf_iocache-t mysys mytap mysys_ssl)
 ADD_DEPENDENCIES(mf_iocache-t GenError)
 MY_ADD_TEST(mf_iocache)
 
+# Json writer needs String which needs sql library
+ADD_EXECUTABLE(my_json_writer-t my_json_writer-t.cc dummy_builtins.cc)
+TARGET_LINK_LIBRARIES(my_json_writer-t sql mytap)
+MY_ADD_TEST(my_json_writer)

unittest/sql/my_json_writer-t.cc

@@ -105,7 +105,6 @@ int main(int args, char **argv)
     ok(w.invalid_json, "Named array in an array");
   }
 
-  // BAD:
   {
     Json_writer w;
     w.start_array();
@@ -113,7 +112,6 @@ int main(int args, char **argv)
     ok(w.invalid_json, "JSON object end of array");
   }
 
-  // BAD:
   {
     Json_writer w;
     w.start_object();