[v1.1.2] Assets batch will overwrite what existed before in `jar`

[liplum]

When I configured the assets batch, the content in jar task output will be overwritten.

mindustryAssets {
    sprites {
        dir = rootDir.resolve("sprites")
        dependsOn("antiAlias")
    }
    sprites {
        dir = rootDir.resolve("sprites/data")
        rootAt(rootDir.resolve("sprites"))
        dependsOn("antiAlias")
        genClass
    }
    sounds {
        dir = rootDir.resolve("sounds")
        genClass
    }
}