configure.in: expand libdir_basename
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39347 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
configure.in: expand libdir_basename
not to defer the expansion till ruby.pc.in and mkmf.rb. [Bug #7874]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39347 b2dd03c8-39d4-4d8f-98ff-823fe69b080e