Fix `make dev` when the `bin/` directory doesn't exist.
Fix `make dev` when the `bin/` directory doesn't exist.

Without this patch you end up with a nifty consul build named `bin`,
not `bin/consul`.

zeroae/consul,tshak/consul,i0rek/consul,dankraw/consul,calgaryscientific/consul,calgaryscientific/consul,leowmjw/consul,sweeneyb/consul,tugbabodrumlu/consul,sweeneyb/consul,pmalmgren/consul,vamage/consul,42wim/consul,hashicorp/consul,calgaryscientific/consul,scalp42/consul,tugbabodrumlu/consul,calgaryscientific/consul,vamage/consul,pmalmgren/consul,leowmjw/consul,kingland/consul,dankraw/consul,kingland/consul,sweeneyb/consul,youhong316/consul,hashicorp/consul,scalp42/consul,i0rek/consul,kingland/consul,i0rek/consul,rhyas/consul,pmalmgren/consul,sweeneyb/consul,dankraw/consul,42wim/consul,zeroae/consul,pmalmgren/consul,youhong316/consul,vamage/consul,zeroae/consul,zeroae/consul,tshak/consul,tugbabodrumlu/consul,tugbabodrumlu/consul,tugbabodrumlu/consul,zeroae/consul,youhong316/consul,scalp42/consul,sweeneyb/consul,calgaryscientific/consul,42wim/consul,vamage/consul,scalp42/consul,hashicorp/consul,rhyas/consul,youhong316/consul,dankraw/consul,kingland/consul,tshak/consul,kingland/consul,rhyas/consul,scalp42/consul,rhyas/consul,tshak/consul,i0rek/consul,tshak/consul,pmalmgren/consul,leowmjw/consul,youhong316/consul,i0rek/consul,42wim/consul,hashicorp/consul,leowmjw/consul,42wim/consul,vamage/consul,leowmjw/consul,rhyas/consul,dankraw/consul