ci: add Dockerfile for Ubuntu 16.04

Added a Dockerfile which captures all the necessary dependencies to
build Xen on a Ubuntu 16.04 system.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

automation/build/ubuntu/xenial.dockerfile

@@ -0,0 +1,47 @@
+FROM ubuntu:16.04
+LABEL maintainer.name="The Xen Project " \
+      maintainer.email="xen-devel@lists.xenproject.org"
+
+ENV DEBIAN_FRONTEND=noninteractive
+ENV USER root
+
+RUN mkdir /build
+WORKDIR /build
+
+# build depends
+RUN apt-get update && \
+    apt-get --quiet --yes install \
+        build-essential \
+        zlib1g-dev \
+        libncurses5-dev \
+        libssl-dev \
+        python2.7-dev \
+        xorg-dev \
+        uuid-dev \
+        libyajl-dev \
+        libaio-dev \
+        libglib2.0-dev \
+        clang \
+        libpixman-1-dev \
+        pkg-config \
+        flex \
+        bison \
+        gettext \
+        acpica-tools \
+        bin86 \
+        bcc \
+        liblzma-dev \
+        libc6-dev-i386 \
+        libnl-3-dev \
+        ocaml-nox \
+        libfindlib-ocaml-dev \
+        markdown \
+        transfig \
+        pandoc \
+        checkpolicy \
+        wget \
+        git \
+        && \
+        apt-get autoremove -y && \
+        apt-get clean && \
+        rm -rf /var/lib/apt/lists* /tmp/* /var/tmp/*