Add dockerfile integration test

.github/workflows/integration.yml

@@ -92,6 +92,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          repository: ${{ matrix.repo.name }}
+          ref: ${{ matrix.repo.ref }}
+          path: repo
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v1
@@ -104,7 +108,7 @@ jobs:
           echo 'RUN apt-get update -qq && \' >> Dockerfile.issue
           echo '    apt-get install -y libclang-dev' >> Dockerfile.issue
           echo 'COPY Gemfile.issue /app/Gemfile' >> Dockerfile.issue
-          echo "RUN git clone https://github.com/oxidize-rb/rb-sys /rb_sys && cd /rb_sys && git checkout $GITHUB_SHA && git rev-parse HEAD" >> Dockerfile.issue
+          echo "ADD ./repo/ /rb_sys" >> Dockerfile.issue
           echo 'ENV RUBYOPT=-I/rb_sys/gem/lib' >> Dockerfile.issue
           echo 'RUN bundle install' >> Dockerfile.issue
           cat Dockerfile.issue