common.mk: RUBY_TESTOPTS
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49725 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
common.mk: RUBY_TESTOPTS
RUBY_TESTOPTS, which is prefixed to get rid of conflict.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49725 b2dd03c8-39d4-4d8f-98ff-823fe69b080e