dirDeleteFilePosix

fn dirDeleteFilePosix(userdata: ?*anyopaque, dir: Dir, sub_path: []const u8) Dir.DeleteFileError!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, 0))) {
            .SUCCESS => {
                syscall.finish();
                return;
            },
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            // Some systems return permission errors when trying to delete a
            // directory, so we need to handle that case specifically and
            // translate the error.
            .PERM => switch (native_os) {
                .driverkit, .ios, .maccatalyst, .macos, .tvos, .visionos, .watchos, .freebsd, .netbsd, .dragonfly, .openbsd, .illumos => {

                    // Don't follow symlinks to match unlinkat (which acts on symlinks rather than follows them).
                    var st = std.mem.zeroes(posix.Stat);
                    while (true) {
                        try syscall.checkCancel();
                        switch (posix.errno(fstatat_sym(dir.handle, sub_path_posix, &st, posix.AT.SYMLINK_NOFOLLOW))) {
                            .SUCCESS => {
                                syscall.finish();
                                break;
                            },
                            .INTR => continue,
                            else => {
                                syscall.finish();
                                return error.PermissionDenied;
                            },
                        }
                    }
                    const is_dir = st.mode & posix.S.IFMT == posix.S.IFDIR;
                    if (is_dir)
                        return error.IsDir
                    else
                        return error.PermissionDenied;
                },
                else => {
                    syscall.finish();
                    return error.PermissionDenied;
                },
            },
            else => |e| {
                syscall.finish();
                switch (e) {
                    .ACCES => return error.AccessDenied,
                    .BUSY => return error.FileBusy,
                    .FAULT => |err| return errnoBug(err),
                    .IO => return error.FileSystem,
                    .ISDIR => return error.IsDir,
                    .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 => |err| return errnoBug(err), // Not passing AT.REMOVEDIR
                    .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),
                }
            },
        }
    }
}