tests/docker: add ubuntu 18.04

Based on the ubuntu.docker file.
Used to reproduce the build failure Peter was seeing.
Others might find this useful too ;)

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20190503070241.24786-1-kraxel@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

tests/docker/dockerfiles/ubuntu1804.docker

@@ -0,0 +1,57 @@
+FROM ubuntu:18.04
+ENV PACKAGES flex bison \
+    ccache \
+    clang \
+    gcc \
+    gettext \
+    git \
+    glusterfs-common \
+    libaio-dev \
+    libattr1-dev \
+    libbluetooth-dev \
+    libbrlapi-dev \
+    libbz2-dev \
+    libcacard-dev \
+    libcap-dev \
+    libcap-ng-dev \
+    libcurl4-gnutls-dev \
+    libdrm-dev \
+    libepoxy-dev \
+    libfdt-dev \
+    libgbm-dev \
+    libgtk-3-dev \
+    libibverbs-dev \
+    libiscsi-dev \
+    libjemalloc-dev \
+    libjpeg-turbo8-dev \
+    liblzo2-dev \
+    libncurses5-dev \
+    libncursesw5-dev \
+    libnfs-dev \
+    libnss3-dev \
+    libnuma-dev \
+    libpixman-1-dev \
+    librados-dev \
+    librbd-dev \
+    librdmacm-dev \
+    libsasl2-dev \
+    libsdl2-dev \
+    libseccomp-dev \
+    libsnappy-dev \
+    libspice-protocol-dev \
+    libspice-server-dev \
+    libssh2-1-dev \
+    libusb-1.0-0-dev \
+    libusbredirhost-dev \
+    libvdeplug-dev \
+    libvte-2.91-dev \
+    libxen-dev \
+    make \
+    python-yaml \
+    sparse \
+    texinfo \
+    xfslibs-dev
+RUN apt-get update && \
+    apt-get -y install $PACKAGES
+RUN dpkg -l $PACKAGES | sort > /packages.txt
+ENV FEATURES clang pyyaml sdl2