gitlab-ci: Add ccache to docker image, and leave in autotools

We're going to make use of these in build & test jobs.

.gitlab-ci.yml

@@ -13,7 +13,7 @@
 # container registry, so that the image from the main repository's registry
 # will be used there as well.
 variables:
-    IMAGE_TAG: "debian-testing-20181217"
+    IMAGE_TAG: "debian-testing-20190219"
     IMAGE_LOCAL: "$CI_REGISTRY_IMAGE:$IMAGE_TAG"
     IMAGE_MAIN: "registry.freedesktop.org/xorg/xserver:$IMAGE_TAG"
 

.gitlab-ci/Dockerfile

@@ -12,7 +12,7 @@ RUN export DEBIAN_FRONTEND=noninteractive; \
     chmod +x /usr/sbin/policy-rc.d && \
     echo 'deb-src https://deb.debian.org/debian testing main' >/etc/apt/sources.list.d/deb-src.list && \
     apt-get update && \
-    apt-get install -y meson git ca-certificates cmake automake autoconf libtool libwaffle-dev \
+    apt-get install -y meson git ca-certificates ccache cmake automake autoconf libtool libwaffle-dev \
         libxkbcommon-dev python3-mako python3-numpy python3-six x11-utils x11-xserver-utils xauth xvfb && \
     apt-get build-dep -y xorg-server && \
     \
@@ -29,7 +29,7 @@ RUN export DEBIAN_FRONTEND=noninteractive; \
     echo '[xts]' > piglit/piglit.conf && echo 'path=/root/xts' >> piglit/piglit.conf && \
     find -name \*.a -o -name \*.o | xargs rm && \
     \
-    apt-get purge -y git cmake automake autoconf libtool libwaffle-dev libxkbcommon-dev \
+    apt-get purge -y git cmake libwaffle-dev libxkbcommon-dev \
         x11-utils x11-xserver-utils xauth xvfb && \
     apt-get autoremove -y --purge && apt-get clean && \
     rm -f /var/lib/apt/lists/deb.debian.org_debian_dists_testing_*