If you are born in Ghana to parents who are not Ghanaian citizens, you are not considered a Ghanaian citizen by birth.  According to Nigerian law, a person is considered a Nigerian citizen by birth if:

1. They were born in Nigeria and at least one parent or grandparent is a Nigerian citizen.
2. They were born outside Nigeria but at least one parent is a Nigerian citizen.

In this scenario, the person was born in Ghana to Nigerian parents. This means that, under Nigerian law, the person is a Nigerian citizen by birth because his/her parents are Nigerian citizens, regardless of location of birth. So, even though the person was born in Ghana, the citizenship follows the nationality of his/her parents, making the person a Nigerian citizen by birth.