Add node graph building and game parameters for cubemaps

[WonderlandWar]

Just a small extra convenience, you'd probably need to have it load into the game to build the node graphs (building cubemaps doesn't build node graphs for some reason despite loading into the map)

For cubemaps, I do think it would be nice to add custom game parameters when the game starts. Like +building_cubemaps, for example.

[Exactol]

Not familiar with node graphs, would the nav step create it?

[WonderlandWar]

Not familiar with node graphs, would the nav step create it?

Not sure, but I think what you could do is have the map start to build the node graphs, and to detect when the node graphs are done rebuilding, you can detect if the .ain file changes and if it does, it's likely done building the node graphs.