I've tried the hda-jack-retask tool, but I couldn't get it working quite right, and the program itself seems quite buggy. On Windows, it's possible to do this on the Realtek audio panel, and I wanted to do the same on Linux.
I'm running Ubuntu Gnome 15.10, with kernel 4.4.2. My motherboard is a Gigabyte P35-DS3L (rev 2.0), and I am using the onboard audio.