Suppose Libland is a libertarian state. The occupants of Libland stay alive by eating Food. Xia is another state. For whatever reason, they don't like Libland, and for whatever reason, they can produce Food much more cheaply than Libland.
Xia starts flooding the Libland market with cheap Food, so that it's is uneconomic for anyone in Libland to produce Food, and the Food industry disappears.
Suddenly Xia cuts of Libland's food supply, and invades several days later. Libland has no means of producing food in short order, and they cannot buy it from anyone else for some reason (for example Xia is the only other state, or it would take too long to open trading routes with other states).
How does Libertarianism cope with this situation?
[edit: please don't treat me as stupid or a troll. I genuinely want to understand libertarianism, and extreme counter-examples are a method of understanding that I find very helpful]