An activist investor is building a stake in Dole PLC. Jan Barta is a high-profile Czech investor. He now owns 5.2 per cent of the business, about $49 million worth.  For his day job, Barta is a partner at Pale Fire Capital, a private equity fund specialising in technology companies. But Barta’s investment in Dole doesn’t seem to be related to Pale Fire Capital.  According to the 13-D form, the stake has been acquired with “personal funds”. Though you’d have to wonder how wealthy a person would have to be to put $49 million of their own money into one…