Train tracks dismantled and rebuilt in front of moving train?

Possibly Trolley Ahoy from 1936 by Van Beuren studios. The irritable Mister Bang makes a wager with the Skipper that operates the trolley that the Skipper can't get Mister Bang to his connecting train on time. Despite some hijinks en route, the Skipper nearly succeeds, but the train has already departed. Fortunately, the Skipper's wife Katrinka is a living deus ex machina who brings the train back to Mister Bang by reeling in its tracks hand over hand like a length of rope. Mister Bang makes his connecting train, and grudgingly pays off his bet.

It's not cel animated, but rather stop motion, but such a scene occurs in Aardman Animation's Wallace and Gromit cartoon The Wrong Trousers from 1993. In order to catch up to fleeing thief Feathers McGraw, Wallace and Gromit ride a model train that runs throughout their house as a kind of lazybones delivery system. However, when the pair's locomotive gets shunted onto a dead-end spur, Gromit grabs a box of track sections, and builds additional track in front of their moving train with incredible speed and precision.

There's also the more recent The Iron Giant from 1999, directed by Brad Bird. At one point, the Giant sees some railroad tracks, and begins chowing down on them like up-for-grabs licorice. When Hogarth whinges that the tracks have to be put back, the Giant does so, but fusses too long lining them up correctly, and gets struck by a speeding train.