Use a base image for building kernel

As we do not have a simple way to hash Debian, use the Docker
sha256 until we switch to Alpine.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

alpine/base/debian-build-kernel/Dockerfile

@@ -0,0 +1,24 @@
+FROM debian:jessie
+
+RUN apt-get update && apt-get -y upgrade && apt-get -y install \
+  unzip \
+  xz-utils \
+  curl \
+  bc \
+  build-essential \
+  cpio \
+  gcc libc6 libc6-dev \
+  kmod \
+  squashfs-tools \
+  genisoimage \
+  xorriso \
+  syslinux \
+  isolinux \
+  automake \
+  pkg-config \
+  git \
+  ncurses-dev \
+  p7zip-full \
+  lzop \
+  wget \
+  vim