[rubygems/rubygems] Get rake package tested

https://github.com/rubygems/rubygems/commit/006cdd4084

test/rubygems/test_rake_package.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+require "rubygems/test_case"
+require "open3"
+
+class TestRakePackage < Minitest::Test
+
+  def test_builds_ok
+    output, status = Open3.capture2e("rake package")
+
+    assert_equal true, status.success?, "Expected `rake package` to work, but got errors: #{output}"
+  end
+
+end