mspec.rb: keep jobserver fds

* spec/mspec/lib/mspec/commands/mspec.rb (MSpecMain#run): do not
  close jobserver FDs for mspec-run.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59166 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/mspec/lib/mspec/commands/mspec.rb

@@ -159,7 +159,7 @@ class MSpecMain < MSpecScript
       exit multi_exec(argv)
     else
       $stderr.puts "$ #{argv.join(' ')}"
-      exec(*argv)
+      exec(*argv, close_others: false)
     end
   end
 end