oddity building ports with archiving

[Jeremy Lavergne]

>>   I've noticed an oddity while building local ports under MacPorts  
>> 1.8.0 with the archiving feature enabled.
>
>>   [...] Otherwise
>> when archive is enabled it seems one has to constantly delete the  
>> archive manually between builds. Or am I missing something here?
>
> This is a change introduced with MacPorts 1.8.0, as previously it  
> would overwrite the old archive:
> ...
> So yeah, you will have to clean it manually - there is no "force" or  
> "rearchive" option yet.

To do so:
sudo port clean --archive PORTNAME