[lokisetup] More fun...

[Ryan C. Gordon]

>  uncompress
> You can optionally manually uncompress (or otherwise post-process) a
> file through an arbitrary shell command specified in this tag. %s in the
> string will be substituted with the actual file name. The current
> directory for the command will be that of the directory containing the
> file to be processed.

We seem to be:

 1) Copying the compressed file to the right location.
 2) Running the shell command in the dir we copied from.
 3) Trying to update the md5sum from an attribute that doesn't take
    installation dir into account.

Fixes:
 - Run shell command in dir we copied to. There's not much point to
copying the file if we're not going to process it.  :)
 - "target" is relative to dir we copied from.

If that's cool, let me know and I'll commit.

--ryan.