Help creating a PR to add a kernel feature for openwrt-bird

I had opened a Github issue to add TCP_MD5SIG support for bird-openwrt -
Today, I was told on IRC to "send a PR for packages repo that adds it"

Running make kernel_menuconfig shows the module available under TCP/IP networking - CONFIG_TCP_MD5SIG so I thought this might not be that hard to package as a kmod.

But as this cannot be built as a module, what are my options here?