* tool/make-snapshot: use ENV["AUTOCONF"] instead of directly using
  literal "autoconf".

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40935 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-05-27

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40936 b2dd03c8-39d4-4d8f-98ff-823fe69b080e