Fix bundled gems locations

Changed since 55bf0ef1aa.

test/runner.rb

@@ -5,7 +5,7 @@ ENV["GEM_SKIP"] = ENV["GEM_HOME"] = ENV["GEM_PATH"] = "".freeze
 ENV.delete("RUBY_CODESIGN")
 
 # Get bundled gems on load path
-Dir.glob("#{__dir__}/../gems/*/*.gemspec")
+Dir.glob("#{__dir__}/../.bundle/gems/*/*.gemspec")
   .reject {|f| f =~ /minitest|test-unit|power_assert/ }
   .map {|f| $LOAD_PATH.unshift File.join(File.dirname(f), "lib") }