Recent apple machines describe themselves being x86_64h. That
architecture is somehow supported by their C compiler and at least
by recent clang. However config.sub does not know that fact so
making universal binary targeting it is rejected by the program.
Why not skip the check by config.sub. [fix GH-1971]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64905 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
