There's not an "easy" way that I'm familiar with.  You could do this:

Create a color map, initializing everything to black.
Run a DFS on the reverse graph with libfoobar as the root.
For every vertex visited by the DFS, change its color to white.
Run topological sort on the original map.

This *might* do what you want. It basically disables vertices that aren't parents of the target. You'd have to see how the topological_sort algorithm actually deals with colors to be certain.