By David Welch Bloomberg News/TNS General Motors Co. has agreed to supply its hydrogen fuel-cell system to Navistar Internatonal Corp. as the semi-truck maker rolls out plans to build a zero-emission long-haul freight business starting in 2024. The move is sure to have a ripple effect on competitors including startup Nikola Corp., which also has an agreement to buy GM’s fuel-cell system for its own planned freight trucks starting in late 2023. GM initially signed a tentative agreement to take a stake in Nikola and help the company develop its trucks, but the two sides scaled back their cooperative ambitions to a simple supply agreement in November.