Remove sensinode build artifacts from .gitignore
Remove sensinode build artifacts from .gitignore

This is part of a set of commits that will obsolete the Sensinode platform

arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,arurke/contiki,arurke/contiki,arurke/contiki,arurke/contiki,arurke/contiki,MohamedSeliem/contiki,arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki