rbinstall.rb: install just one gemspec [ci skip]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56070 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
rbinstall.rb: install just one gemspec [ci skip]
directory only. some gems, (e.g., json) have multiple gemspec
files.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56070 b2dd03c8-39d4-4d8f-98ff-823fe69b080e