RegisterResourceBuildTaskFactory

Registers a build task factory for resources.
The function should return an object (msgpack map) with the following fields:

{
// returns whether the specific resource should be built
shouldBuild = func(resourceName: string): bool,

// asynchronously start building the specific resource.
// call cb when completed
build = func(resourceName: string, cb: func(success: bool, status: string): void): void
}