Can build linuxkit for 4.14.x (#21)

Update linuxkit builder to build in tree based on linuxkit kernel dev best practices

.gitignore

@@ -0,0 +1 @@
+.idea

src/linuxkit-build.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+#
+# Copyright The Titan Project Contributors.
+#
+
+set -xe
+
+. $(dirname $0)/common.sh
+
+get_zfs_source
+
+cd /src/zfs
+sh ./autogen.sh
+./configure
+make -j8
+make install DESTDIR=/build

src/linuxkit.sh

@@ -6,44 +6,47 @@
 #
 # Get linuxkit-specific source. With linuxkit, the canonical data source is through
 # docker images, so we launch a docker container and then copy out the data we need.
-# The linuxkit images have no usable binaries, so we launch with a command that we
-# know will fail, and then simply ignore the failure. The container will persist
-# in the stopped state so we can copy the necessary data out of it.
+# The linuxkit images have no usable binaries, so we launch an alpine container from
+# the linuxkit kernel image with the required zfs build dependencies.
 #
-function get_kernel() {
-    local container_name=zfs-builder-$(generate_random_string 8)
-    docker run --name $container_name linuxkit/kernel:$KERNEL_VERSION /ignore || /bin/true
-    cd /
-    docker cp $container_name:kernel-dev.tar .
-    docker cp $container_name:kernel.tar .
-    bsdtar xf kernel-dev.tar
-    bsdtar xf kernel.tar
-    rm kernel-dev.tar kernel.tar
 
-    cd /src
-    docker cp $container_name:linux.tar.xz .
-    bsdtar xf linux.tar.xz
-    rm linux.tar.xz
+function build() {
+    local linuxkit_release
 
-    #
-    # Some versions of linuxkit apparently leave the built gcc plugins in the
-    # kernel tree, which can then generate errors because it's looking for
-    # symbols or libraries that might not exist on this system. Build works
-    # fine without them, so blow them away if they happen to be there.
-    #
-    rm -f /usr/src/*/scripts/gcc-plugins/*.so
-    rm -f /usr/src/*/scripts/gcc-plugins/*.o
+    mkdir /docker
+    cp /*.sh /docker
 
+    cat > /docker/Dockerfile <<EOF
+FROM linuxkit/kernel:$KERNEL_VERSION AS ksrc
+FROM linuxkit/alpine:e2391e0b164c57db9f6c4ae110ee84f766edc430 AS build
+RUN apk update
+RUN apk add bash \
+    attr-dev \
+    autoconf \
+    automake \
+    build-base \
+    gettext-dev \
+    git \
+    gettext-dev \
+    linux-headers \
+    libtirpc-dev \
+    libintl \
+    libtool \
+    libressl-dev \
+    util-linux-dev \
+    zlib-dev \
+    zfs-libs
+COPY --from=ksrc /kernel-dev.tar /
+RUN tar xf kernel-dev.tar
+COPY *.sh /
+CMD /linuxkit-build.sh
+EOF
+    local image_name=zfs-builder-linuxkit:$(generate_random_string 8)
+    cd /docker && docker build -t $image_name .
+    local container_name=zfs-builder-$(generate_random_string 8)
+    docker run --name $container_name -e KERNEL_RELEASE=$KERNEL_RELEASE \
+        -e KERNEL_SRC=/src/linux -e KERNEL_OBJ=/lib/modules/$KERNEL_RELEASE/build $image_name
+    docker cp $container_name:/build /
     docker rm $container_name
-
-    KERNEL_SRC=/src/linux
-    KERNEL_OBJ=/lib/modules/$KERNEL_RELEASE/build
-}
-
-function build() {
-    get_zfs_source
-    if [ "$ZFS_CONFIG" != "user" ]; then
-        get_kernel
-    fi
-    build_zfs
+    docker rmi $image_name
 }