project: Add Flatpak CI

.gitlab-ci.yml

+stages:
+- test
+
+flatpak:
+    image: registry.gitlab.gnome.org/gnome/gnome-runtime-images/gnome:master
+    stage: test
+
+    variables:
+        # Replace with your manifest path
+        MANIFEST_PATH: "build-aux/flatpak/org.gnome.Notes.json"
+        RUNTIME_REPO: "https://sdk.gnome.org/gnome-nightly.flatpakrepo"
+        # Replace with your application name, as written in the manifest
+        FLATPAK_MODULE: "bijiben"
+        # Make sure to keep this in sync with the Flatpak manifest, all arguments
+        # are passed except the config-args because we build it ourselves
+        # CONFIGURE_ARGS: "-Dtests=all"
+
+    script:
+        - flatpak-builder --stop-at=${FLATPAK_MODULE} app ${MANIFEST_PATH}
+        - flatpak build app meson --prefix=/app ${CONFIGURE_ARGS} _build
+        - flatpak build app ninja -C _build install
+        # Run tests inside the Flatpak env emulating a display
+        - xvfb-run -a -s "-screen 0 1024x768x24" flatpak build app ninja -C _build test
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