dirDeleteDirPosix

fn dirDeleteDirPosix(userdata: ?*anyopaque, dir: Dir, sub_path: []const u8) Dir.DeleteDirError!void {
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;

    var path_buffer: [posix.PATH_MAX]u8 = undefined;
    const sub_path_posix = try pathToPosix(sub_path, &path_buffer);

    const syscall: Syscall = try .start();
    while (true) {
        switch (posix.errno(posix.system.unlinkat(dir.handle, sub_path_posix, posix.AT.REMOVEDIR))) {
            .SUCCESS => {
                syscall.finish();
                return;
            },
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            else => |e| {
                syscall.finish();
                switch (e) {
                    .ACCES => return error.AccessDenied,
                    .PERM => return error.PermissionDenied,
                    .BUSY => return error.FileBusy,
                    .FAULT => |err| return errnoBug(err),
                    .IO => return error.FileSystem,
                    .ISDIR => |err| return errnoBug(err),
                    .LOOP => return error.SymLinkLoop,
                    .NAMETOOLONG => return error.NameTooLong,
                    .NOENT => return error.FileNotFound,
                    .NOTDIR => return error.NotDir,
                    .NOMEM => return error.SystemResources,
                    .ROFS => return error.ReadOnlyFileSystem,
                    .EXIST => |err| return errnoBug(err),
                    .NOTEMPTY => return error.DirNotEmpty,
                    .ILSEQ => return error.BadPathName,
                    .INVAL => |err| return errnoBug(err), // invalid flags, or pathname has . as last component
                    .BADF => |err| return errnoBug(err), // File descriptor used after closed.
                    else => |err| return posix.unexpectedErrno(err),
                }
            },
        }
    }
}