* `doc/langref` formatting
 * upgrade `.{ .path = "..." }` to `b.path("...")`
 * avoid using arguments named `self`
 * make `Build.Step.Id` usage more consistent
 * add `Build.pathResolve`
 * use `pathJoin` and `pathResolve` everywhere
 * make sure `Build.LazyPath.getPath2` returns an absolute path