Handle pkg path properly for generating local repo when PKGDEST is set

Hi again!

Now if PKGDEST is set, the local repo generation fails because (obviously) the pkg files are not present in the current folder anymore. (Should have tested it properly earlier).

This patch handles the above by cd'ing to PKGDEST. But now _all_ packages present in that folder are added.

Can you think of a better way of doing this?

Regards