Add GitLab CI pipeline

Add a GitLab CI build pipeline, using the two-stage CI templates from
Wayland. This allows us to do really quick builds of Monado itself,
insulating ourselves from the longer and more failure-prone parts of
pulling and building our dependencies.

.gitlab-ci.yml

@@ -0,0 +1,29 @@
+variables:
+  UPSTREAM_REPO: monado/monado
+  DEBIAN_VERSION: buster
+  DEBIAN_TAG: '2019-03-19.0'
+  DEBIAN_CONTAINER_IMAGE: $CI_REGISTRY_IMAGE/debian/$DEBIAN_VERSION:$DEBIAN_TAG
+  DEBIAN_DEBS: build-essential git cmake meson ninja-build doxygen graphviz libeigen3-dev curl patch python3 pkg-config libx11-dev libxxf86vm-dev libxrandr-dev libxcb-randr0-dev libhidapi-dev libwayland-dev libvulkan-dev glslang-dev glslang-tools libglvnd-dev libgl1-mesa-dev ca-certificates
+  DEBIAN_EXEC: 'bash .gitlab-ci/build-openxr-openhmd.sh'
+
+include:
+  - project: 'wayland/ci-templates'
+    ref: c73dae8b84697ef18e2dbbf4fed7386d9652b0cd
+    file: '/templates/debian.yml'
+
+stages:
+  - container_prep
+  - build
+
+container_prep:
+  extends: .debian@container-ifnot-exists
+  stage: container_prep
+
+build-cmake:
+  stage: build
+  image: $DEBIAN_CONTAINER_IMAGE
+  script:
+  - mkdir build
+  - pushd build
+  - cmake -GNinja ..
+  - ninja

.gitlab-ci/build-openxr-openhmd.sh

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+#!/bin/sh
+
+# Install the OpenXR SDK, whatever version, with @haagch's patch so we can
+# actually install it system-wide.
+git clone https://github.com/KhronosGroup/OpenXR-SDK
+pushd OpenXR-SDK
+curl 'https://aur.archlinux.org/cgit/aur.git/plain/support_installing_the_loader.diff?h=openxr-loader-git' | patch -p1
+mkdir build
+pushd build
+cmake -DCMAKE_INSTALL_PREFIX=/usr/local -DCMAKE_INSTALL_LIBDIR=lib -DCMAKE_BUILD_TYPE=Release -DBUILD_TESTS=Off -DPRESENTATION_BACKEND=xlib -DDYNAMIC_LOADER=ON -DOpenGL_GL_PREFERENCE=GLVND -GNinja ..
+ninja install
+popd
+popd
+
+# Install OpenHMD from git master, as released versions are not sufficient
+# for us to build.
+git clone https://github.com/OpenHMD/OpenHMD
+pushd OpenHMD
+mkdir build
+meson --prefix=/usr/local --libdir=lib build
+ninja -C build install
+popd