Use bundler-cache in setup-ruby

Author: sue445

.github/workflows/build.yml

@@ -123,16 +123,7 @@ jobs:
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}
-          bundler-cache: false
-
-      # FIXME: setup-go installs cache in `vendor/` and setup-ruby installs cache in `vendor/bundle/`
-      #        If we use the cache in setup-go and setup-ruby at the same time, this doesn't work well because they use the same directory.
-      #        Therefore, the installation location needs to be changed from the setup-ruby default.
-      - name: bundle install
-        run: |
-          set -xe
-          bundle config --local path ruby-vendor/bundle
-          bundle install --jobs 4
+          bundler-cache: true
 
       - name: export CGO_CFLAGS for golangci-lint
         run: bundle exec rake go:build_envs[CGO_CFLAGS] >> $GITHUB_ENV