Depends on what other choices and freedom of movement the robot has.

It might be able to invoke the third law's exception and give its life to save all the humans. (Are there any on the trolley? That might affect things. It doesn't say one way or the other in the memes.)

Maybe it doesn't have to give its life. It might be strong enough to lift the trolley from the tracks and set it down ensuring anyone on the trolley doesn't come to harm.

But assuming the robot must not leave the spot by the lever and has no non-human-like special abilities, I think the first law has a gaping hole in it. It says it cannot harm a human or through inaction cause a human to come to harm. This means the robot throws the lever, whatever position it was in previously. Because then it has acted.

The fact that other humans come to harm as a result is not the robot's fault, it's the trolley's, and it acted to prevent harm.