test: add a downstream integration test job for nokogiri

Related to #758

.gitlab-ci.yml

@@ -298,3 +298,9 @@ pages:
       - public/devhelp/*.xsl
   only:
     - master@GNOME/libxml2
+
+downstream-nokogiri:
+  # owner: @flavorjones
+  image: ghcr.io/sparklemotion/nokogiri-test:upstream-libxml
+  script:
+    - .gitlab-ci/downstream-nokogiri.sh

.gitlab-ci/downstream-nokogiri.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+set -e
+
+export LIBXML_DIR=$(pwd)
+export MAKEFLAGS=-j$(nproc)
+export NOCONFIGURE=1
+./autogen.sh
+
+git clone https://github.com/sparklemotion/nokogiri
+cd nokogiri
+bundle install
+bundle exec rake compile -- --with-xml2-source-dir=${LIBXML_DIR}
+bundle exec rake test