configure.in: exit with failure

* configure.in (rb_cv_broken_backtrace): exit with failure
  normally, no needs to abort.  [ruby-core:63678] [Bug #10008]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46796 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-07-13

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46797 b2dd03c8-39d4-4d8f-98ff-823fe69b080e