[gnome-menus] ci: add menu-validation test

[Jeremy Bicha <jbicha src gnome org>]

commit d94eb457ee9f0407c714f56d04f68600dab6de8f
Author: Jeremy Bicha <jbicha ubuntu com>
Date:   Fri Jan 25 20:52:57 2019 -0500

    ci: add menu-validation test
    
    This would have caught our recent mistake

 .gitlab-ci.yml | 12 ++++++++++++
 1 file changed, 12 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
new file mode 100644
index 0000000..c06ad0d
--- /dev/null
+++ b/.gitlab-ci.yml
@@ -0,0 +1,12 @@
+validate-menu:
+  image: 'registry.gitlab.gnome.org/gnome/gnome-runtime-images/base:latest'
+  # libxml2 doesn't support https yet but the spec is only available via https
+  # https://bugzilla.gnome.org/791220
+  # https://gitlab.freedesktop.org/freedesktop/freedesktop/issues/114
+  # We shouldn't add the dtd to our git repo because it doesn't have
+  # a clearly distributable license
+  before_script:
+    - dnf install -y wget
+  script:
+    - wget https://standards.freedesktop.org/menu-spec/menu-latest.dtd
+    - xmllint --noblanks --noout --path menu-latest.dtd layout/gnome-applications.menu