common.mk: update-gems for older BASERUBY
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47904 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
common.mk: update-gems for older BASERUBY
add the tool directory to load paths, for older BASERUBY.
[Bug #10372][ruby-core:65630]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47904 b2dd03c8-39d4-4d8f-98ff-823fe69b080e