This file is missing a line at the end to indicate the board variant:
The subfolder must also contain the standard variant with the corresponding pins_arduino.h file.
So, follow the instructions in the tutorial to open your sketchbook folder and create the subfolder \hardware\breadboard\ containing the file boards.txt.
Then edit the file boards.txt to add the missing line.
Then create a subfolder \variants\standard\, and copy the file pins_arduino.h from the folder hardware\arduino\variants\standard\ in your Arduino IDE installation.
In Ubuntu 12.10 this is \usr\share\arduino\ when the Arduino IDE is installed using the Ubuntu Software Center.
This will make the compilation work also for gnoduido.