using OBJECTDIR instead of "obj_cooja" + bugfix: allow for externally defined CC
using OBJECTDIR instead of "obj_cooja" + bugfix: allow for externally defined CC

MohamedSeliem/contiki,MohamedSeliem/contiki,arurke/contiki,arurke/contiki,arurke/contiki,MohamedSeliem/contiki,arurke/contiki,arurke/contiki,bluerover/6lbr,MohamedSeliem/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,bluerover/6lbr,MohamedSeliem/contiki,bluerover/6lbr,arurke/contiki,bluerover/6lbr,arurke/contiki,bluerover/6lbr,bluerover/6lbr,bluerover/6lbr