[OE-core] cleanup-workdir

[Andreas Oberritter]

Hello Kai,

because I was low on disk space, I just tried scripts/cleanup-workdir
for the first time. My observations:

1.) It deletes work directories that were built for other machines
(archs) than the current one. I guess the list of architectures to
handle should be queried from bitbake to avoid this.
2.) It doesn't delete work directories of previously deleted recipes.

Regards,
Andreas