dev-build.py: use a smarter default number of CPUs.
dev-build.py: use a smarter default number of CPUs.

idupree/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,Lasercake/Lasercake,idupree/Lasercake,elidupree/Lasercake,elidupree/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,idupree/Lasercake,elidupree/Lasercake,idupree/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,idupree/Lasercake,Lasercake/Lasercake,idupree/Lasercake,idupree/Lasercake,elidupree/Lasercake