configure.in: sitearch
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39202 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
configure.in: sitearch
should use sitearch, not arch. [ruby-dev:46964] [Bug #7823]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39202 b2dd03c8-39d4-4d8f-98ff-823fe69b080e