It’s a hill, not a mountain. It presumably has plants, which could be burned for fuel. It’s possible that there’s no metal in the hill, but he could make the robot out of stone. Once he gets the prototype running, he can search for better materials as it slowly pushes the rock up the hill. He just has to get back before the fuel runs out.
He can build it. It would be pretty hard to do while pushing a boulder up a hill, but he has all the time in the world!
Does he have any suitable raw materials?
It’s a hill, not a mountain. It presumably has plants, which could be burned for fuel. It’s possible that there’s no metal in the hill, but he could make the robot out of stone. Once he gets the prototype running, he can search for better materials as it slowly pushes the rock up the hill. He just has to get back before the fuel runs out.
Of course he could.