Fix debug platform inclusion for Windows

test/setup_bundler_test.rb

@@ -823,6 +823,35 @@ def test_is_resilient_to_gemfile_changes_in_the_middle_of_setup
     end
   end
 
+  def test_composed_bundle_includes_debug
+    Dir.mktmpdir do |dir|
+      Dir.chdir(dir) do
+        File.write(File.join(dir, "Gemfile"), <<~GEMFILE)
+          source "https://rubygems.org"
+        GEMFILE
+
+        env = T.let(nil, T.nilable(T::Hash[String, String]))
+
+        Bundler.with_unbundled_env do
+          capture_subprocess_io do
+            # Run bundle install to generate the lockfile
+            system("bundle install")
+            env = RubyLsp::SetupBundler.new(dir, launcher: true).setup!
+          end
+
+          gemfile_path = File.join(dir, ".ruby-lsp", "Gemfile")
+          assert_match("debug", File.read(gemfile_path))
+
+          _stdout, stderr = capture_subprocess_io do
+            system(T.must(env), "bundle exec ruby -e 'require \"debug\"'")
+          end
+
+          assert_empty(stderr)
+        end
+      end
+    end
+  end
+
   private
 
   def with_default_external_encoding(encoding, &block)