Activist Elliott Investment Management has built a more than 10% stake in Norwegian Cruise Line and plans to push for changes to turn the struggling cruise-ship operator around, according to people familiar with the matter. Elliott, now one of Norwegian’s top investors, is planning to engage with the company to try to help fix its underperformance, the people said. Its brands include the more premium Oceania Cruises and the luxury Regent Seven Seas Cruises.