configure.in: unexpand_shvar

* configure.in (unexpand_shvar): regularize a shell variable by
  unexpanding shell variables in it.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39294 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-02-18

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39295 b2dd03c8-39d4-4d8f-98ff-823fe69b080e