hi Avenue33 and gianmarco
if you get this:
make: *** No rule to make target /Applications/Arduino.app/Contents/Resources/Java/hardware/[u]Sanguino[/u]/cores/arduino/pins_arduino.o', needed by bin/core.a'. Stop.
It means you are trying to compile for sanguino and he can't find a file in the Sanguino folder. In this case you would need to have the sanguino sources in your arduino app. You can find instructions about that here: http://sanguino.cc/
Also, if you are not trying to build for Sanguino, you should change the build setting in XCode to make it build for your specific board. I have put the instructions on how to do that in the Readme inside the XCode project:
https://github.com/timknapen/Arduino-With-XCode/blob/master/Arduino/ArduinoOnXCode4_2/README
And maybe you didn't download the specific project for XCode4 on github. It is called "ArduinoOnXCode4_2" , I just re-uploaded that.
The one called "ArduinoOnXcode/" is the template for XCode 3.2
let me know if it still fails, I can't test on Lion right now because I'm out of the country.
best,
tim