Migrate to workdir version 5 and move already built packages into the edge
channel subdir, for example:
$WORK/packages/x86_64/hello-world-1-r5.apk
to:
$WORK/packages/edge/x86_64/hello-world-1-r5.apk
The build.postmarketos.org code has already been adjusted to find built
packages in either directory structure.