bug#13391: dd silently ignores lseek error

[Paul Eggert]

On 01/08/13 10:11, Neil Klopfenstein wrote:
> Note that it begins reading at the _beginning of the ar file_ -- the 'skip'
> argument has failed silently.

But the 'skip' hasn't failed.  It's merely being implemented via 'read'
rather than via 'lseek'.  The records are being skipped correctly.

It might be useful to give dd a new option, which causes it
to insist on lseeking rather than reading in cases like these,
and to report an error if the lseek fails.