r21312 causes test failures on RubyGems
r21312 causes many failures on RubyGems tests as the attached log.
r21312 is for [ruby-core:20990]. It is sure that RubyGems should not create directories outside of DESTDIR on installing Ruby.
But did r21312 break an assumption for Rubygems' working correctly?
What is the right way to fix [ruby-core:20990]?