gitlab-ci: Add "dist" job to build distribution tarball

Prepare for GNOME Release Service.

.gitlab-ci.yml

@@ -286,6 +286,14 @@ cmake:linux:gcc:shared:
     CC: gcc
     SUFFIX: linux-gcc-shared
 
+dist:
+  image: registry.gitlab.gnome.org/gnome/libxml2
+  script:
+    - sh .gitlab-ci/dist.sh
+  artifacts:
+    paths:
+      - libxml2-dist/*.tar.xz
+
 pages:
   script:
     - mkdir -p public

.gitlab-ci/dist.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+set -e
+
+mkdir -p libxml2-dist
+cd libxml2-dist
+sh ../autogen.sh
+make distcheck V=1 DISTCHECK_CONFIGURE_FLAGS='--with-legacy'
+if [ -z "$CI_COMMIT_TAG" ]; then
+    mv libxml2-*.tar.xz libxml2-git-$CI_COMMIT_SHORT_SHA.tar.xz
+fi