Help building newer batman-adv for old OpenWRT

Hi all,

I really need some help building a recent version of batman-adv (and batctl) for an older build of OpenWRT from around late-2016.

The kernel version is 4.1.23

The most recent version I can get to build is 2017.3, anything after that gives a variety of errors.

I can't update the OpenWRT build as there are too many other customisations to the build that aren't compatible with newer versions.

Any advice would be greatly appreciated.