configure.in: no __builtin_setjmp on x64-mingw

* configure.in: get rid of __builtin_setjmp/__builtin_longjmp on
  x64-mingw, which causes SEGV with callcc.
  [ruby-core:61887] [Bug #9710]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45537 b2dd03c8-39d4-4d8f-98ff-823fe69b080e