Add .gitlab-ci.yml

This builds libvdpau and runs the tests, although the only test at the moment is
dlclose and it is skipped because there is no X server running in the Docker
environment.
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>

.gitlab-ci.yml

+image: docker:latest
+services:
+    - docker:dind
+
+before_script:
+    - echo FROM nwnk/xserver-travis-rawhide:v5 > Dockerfile
+    - echo ADD . /root >> Dockerfile
+    - echo WORKDIR /root >> Dockerfile
+    - docker build -t withgit .
+
+job:
+    script:
+        - docker run --volume $HOME/.ccache:/root/.ccache withgit ./test/gitlab-ci.sh

test/gitlab-ci.sh

+#!/bin/sh
+set -x
+
+meson setup build/
+meson configure -Dprefix=/usr -Ddri2=true build/
+ninja -C build/ install test