Make Docker build run against 5.8-rc2

Dockerfile

@@ -1,14 +1,27 @@
 FROM ubuntu:latest AS build
 
+ARG KVER=5.8
+ARG URL_LINUX_HEADERS=https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.8-rc2/amd64/linux-headers-5.8.0-050800_5.8.0-050800.202006212330_all.deb
+ARG URL_LINUX_HEADERS_GENERIC=https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.8-rc2/amd64/linux-headers-5.8.0-050800-generic_5.8.0-050800.202006212330_amd64.deb
+ARG URL_LINUX_MODULES=https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.8-rc2/amd64/linux-modules-5.8.0-050800-generic_5.8.0-050800.202006212330_amd64.deb
+ARG URL_LINUX_IMAGE=https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.8-rc2/amd64/linux-image-unsigned-5.8.0-050800-generic_5.8.0-050800.202006212330_amd64.deb
+
 ENV WORKDIR /build/
 
 RUN mkdir -p $WORKDIR
 
-WORKDIR $WORKDIR
+WORKDIR /debs
 
 RUN apt-get update
 
-RUN apt-get install -y bc build-essential dkms linux-headers-$(uname -r)
+RUN apt-get install -y bc build-essential dkms linux-headers-$(uname -r) wget linux-base
+
+RUN wget $URL_LINUX_HEADERS $URL_LINUX_HEADERS_GENERIC $URL_LINUX_MODULES $URL_LINUX_IMAGE
+
+RUN dpkg -i ./*.deb
+RUN apt-get install -f
+
+WORKDIR $WORKDIR
 
 FROM build