rake compile explicitly in GHA

Author: hsbt

.github/workflows/test.yml

@@ -37,5 +37,7 @@ jobs:
       with:
         ruby-version: ${{ matrix.ruby }}
         bundler-cache: true # 'bundle install' and cache gems
+    - name: Build
+      run: bundle exec rake compile
     - name: Run test
       run: rake test