configure.in: fix messages
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46222 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
configure.in: fix messages
the message if the macro name is not given. fix up r45608.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46222 b2dd03c8-39d4-4d8f-98ff-823fe69b080e