Saudi Arabia’s sovereign-wealth fund has amassed stakes worth roughly $1 billion in four major European oil companies, according to people familiar with the matter, buying assets it perceives as undervalued in a market depressed by the coronavirus pandemic and low oil prices. The stakes in Equinor ASA, Royal Dutch Shell PLC, Total SA and Eni SpA were all bought by the Public Investment Fund on the open market in recent weeks, said the people, who added that the fund might continue to make stock purchases. …