Traced this https://lists.zx2c4.com/pipermail/wireguard/2017-January/000935.html back from JAN 2017.

The BASH package https://github.com/openwrt/packages/commits/master/utils/bash/patches is available in OpenWRT since at least AUG/SEPT 2014 and could be installed as dependency to wg-quick.

How to get wg-quick manually installed into (working in) OpenWRT after having installed their BASH package?