Add missing ruby/tests/test_ruby_package.proto

Makefile.am

@@ -904,6 +904,7 @@ ruby_EXTRA_DIST=                                                             \
   ruby/tests/stress.rb                                                       \
   ruby/tests/generated_code.proto                                            \
   ruby/tests/test_import.proto                                               \
+  ruby/tests/test_ruby_package.proto                                         \
   ruby/tests/generated_code_test.rb                                          \
   ruby/tests/well_known_types_test.rb                                        \
   ruby/travis-test.sh