util/docker/doc.coreboot.org/Dockerfile: Use alpine:3.8, Sphinx 1.7

With Alpine base, use pip to install Sphinx 1.7 and Sphinx-autobuild
Alpine, a 4.5MB base, is used over Debian Stable, 101MB, to cut down the
total size of the docker image.

Change-Id: I53f246206458b1de34cd7f3a42481b91ca285ff0
Signed-off-by: Tom Hiller <thrilleratplay@gmail.com>
Reviewed-on: https://review.coreboot.org/28211
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/docker/doc.coreboot.org/makeSphinx.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+if [ "$1" == "livehtml" ]; then
+  echo "Starting live documentation build"
+  cd /data-in/Documentation && make livesphinx BUILDDIR=/tmp/build
+else
+  echo "Starting production documentation build"
+  cd /data-in/Documentation \
+    && make sphinx BUILDDIR=/tmp/build \
+    && rm -rf /data-out/* \
+    && mv /tmp/build/html/* /data-out/
+fi