Android 3.18 inline kernel build failure

When building with the latest source that the wireguard importer script fetches (http://WireGuard-0.0.20181218.zip) I am getting this error: AS net/wireguard/crypto/zinc/chacha20/chacha20-arm64.o fixdep: error opening config file:

Re: [ANNOUNCE] WireGuard Snapshot `0.0.20181006` Available

I started getting build errors today with the latest release. I'm building Wireguard in a 3.18.123 kernel using Clang 8.0. Here is the error, any help would be appreciated. net/built-in.o: In function `selftest_run':