Hi Reinier,
on the Rpi, the NIC driver is provided by the USB driver. So 'make drivers/nic' does not produce any meaningul result.
I guess that you are using Genode version where the lwip.run script did not support the Rpi, yet. Please check that your branch has the following commit (which was merged to master after version 14.08):
https://github.com/genodelabs/genode/commit/181d507cf837f1e05c4e352fcbddbc0f...
Alternatively, you could give the current master branch a try, which is known to work.
Cheers Norman