ci: add creek to the downstream pipeline

Author: flavorjones

.github/workflows/downstream.yml

@@ -42,6 +42,9 @@ jobs:
           - url: https://github.com/rails/rails
             name: xmlmini
             command: "cd activesupport && bundle exec rake test TESTOPTS=-n/XmlMini/"
+          - url: https://github.com/pythonicrubyist/creek
+            name: creek
+            command: "bundle exec rake spec"
     runs-on: ubuntu-latest
     container:
       image: ghcr.io/sparklemotion/nokogiri-test:mri-3.1
@@ -63,5 +66,8 @@ jobs:
           else
             echo "gem 'nokogiri', path: '..'" >> Gemfile
           fi
+          if egrep "add_development_dependency.*\bbundler\b" *gemspec ; then
+            sed -i 's/.*add_development_dependency.*\bbundler\b.*//' *gemspec
+          fi
           bundle install --local || bundle install
           ${{matrix.command}}