[pygobject/ci-gtk4] ci: add a gtk4 job. Fixes #249

[Christoph Reiter <creiter src gnome org>]

commit f1ab7c78615ae2761dca02a8e2c11b8bb0a2f88b
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Sat Sep 22 22:03:27 2018 +0200

    ci: add a gtk4 job. Fixes #249

 .gitlab-ci.yml | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 3a25c6a6..6c0d145f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -123,3 +123,10 @@ gnome-master:
   image: registry.gitlab.gnome.org/gnome/gnome-runtime-images/gnome:master
   script:
     - xvfb-run -a flatpak run --filesystem=host --share=network --socket=x11 --command=bash 
org.gnome.Sdk//master -x .gitlab-ci/test-flatpak.sh
+
+gnome-master-gtk4:
+  allow_failure: true
+  stage: build_and_test
+  image: registry.gitlab.gnome.org/gnome/gnome-runtime-images/gnome:master
+  script:
+    - xvfb-run -a flatpak run --env=TEST_GTK_VERSION=4.0 --filesystem=host --share=network --socket=x11 
--command=bash org.gnome.Sdk//master -x .gitlab-ci/test-flatpak.sh