A Macbook with Leopard cannot use sqlite3-ruby or mysql, so no Rails 3 possible on a mac with Leopard?

Question

I have a macbook that has Leopard (OS X 10.5) but don't have Snow Leopard.

It ran Rails 2.3.8 fine, but now when it comes to Rails 3.x, with Ruby 1.9.2 (or 1.8.7), gem install cannot build mysql, mysql2, or sqlite3-ruby, so essentially, this macbook can't use Rails 3.x at all? Is there a way? thanks.

(it seems that the latest Xcode is needed, but it only runs on Snow Leopard)