Problems with Ruby: can’t find header files for ruby on Snow Leopard

A couple of days ago I installed (upgrade actually) my Mac with the Snow Leopard (Mac OX 10.6.2). This was my first migration to the Mac World, before that I just went crazy at the beginning from Win3.11 to Win95 to Win98. After that I just backed up all my files formated the HD and installed a fresh copy of the brand new and “marvelous-solve-all-your-problems” last Windows.
After some time decided to try Ubuntu 7.10 and the migration to 8.04 was just simple without traumas and the same from 8.04 to 8.10.
So, at this time I decided that after a backup using Time Machine I’ll try to upgrade that, and leave behind all the bad memories of the my Windows past tragedies.
All ran gloriously! It took around one hour to migrate from the “old” Leopard - totally upgraded - to the Snow.
For the project that I was in I just needed Java running with all that stuffs such as: JDK6, Eclipse, Spring, Hibernate, MySQL, Oracle, Tomcat, Glassfish. But now that I wanna start a new personal project with Ruby on Rails with Heroku I got a problem installing the Heroku gem:
Actually this is not a problem with Heroku. After some researches I realized that I had on Leopard the XCode installed but I didn’t installed it on the Snow one. The solution? Put the same DVD for the install of the SL and click on the icon to install the XCode.
After the installation I could install the Heroku gem



