runruby.rb: use File::PATH_SEPARATOR
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49762 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
runruby.rb: use File::PATH_SEPARATOR
DYLD_INSERT_LIBRARIES is colon-separated list.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49762 b2dd03c8-39d4-4d8f-98ff-823fe69b080e