Optiplex 7060, network drivers for Ubuntu 14.04

Answer: official binaries do not exist as of this writing. I won't post the binary I got to work because no one in their right mind would trust it, but here's what I did:

Downloaded the driver sources from Intel here: https://downloadcenter.intel.com/download/22283/Ethernet-Intel-Ethernet-Adapter-Complete-Driver-Pack?product=82185

Updated to the most recent kernel backport packages with "sudo apt-get install --install-recommends linux-generic-lts-xenial"

Updated gcc to a more recent version with 'retpoline' support (https://lwn.net/Articles/744287/), to match the newer kernel packages.

Built e1000e-3.4.0.2 from the Intel sources, put it onto the machine via USB stick, replaced the existing e1000e driver under /lib/modules, and added a line with 'e1000e' to /etc/modules.

Added to /etc/network/interfaces:

auto em1
iface em1 inet dhcp