var diren = std.fs.cwd().openDir(dir, .{ .iterate = true }) catch unreachable;
    defer diren.close();

    const io = b.graph.io;
    var diren = std.Io.Dir.cwd().openDir(io, dir, .{ .iterate = true }) catch unreachable;
    defer diren.close(io);

    while (srcs.next() catch unreachable) |src|

    while (srcs.next(io) catch unreachable) |src|