test/ruby/test_rubyoptions.rb: fix race

Signal delivery is not guaranteed to be immediate, a process may
exit before receiving signal it sent itself.

* test/ruby/test_rubyoptions.rb (test_segv_test): fix race

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47971 b2dd03c8-39d4-4d8f-98ff-823fe69b080e