make: emit explanation for /api isolation
make: emit explanation for /api isolation

Emit a slightly helpful message when /api depends on nomad internal
packages.

burdandrei/nomad,burdandrei/nomad,burdandrei/nomad,dvusboy/nomad,burdandrei/nomad,burdandrei/nomad,burdandrei/nomad,dvusboy/nomad,dvusboy/nomad,hashicorp/nomad,hashicorp/nomad,hashicorp/nomad,dvusboy/nomad,hashicorp/nomad,dvusboy/nomad,hashicorp/nomad,hashicorp/nomad,dvusboy/nomad,dvusboy/nomad,burdandrei/nomad