when running something like 'ROOT=/build/target1 emerge uclibc baselayout-lite busybox' and when /build/target1 is empty, portage creates several directories like /var/cache, etc. however it fails to create /var/lib/portage (actually, ${ROOT}/var/lib/portage). without this dir, the world file never gets created.
there is code to create it (in portage.py) but it seems there's a few codepaths that can execute w/out hitting the /var/lib/portage creation code
Fixed on or before 2.0.51.22-r1
Looking through the batch of bugs, I'm not sure that some of these are actually fixed in stable. Others, the requirements have possibly changed after the initial fix was committed. If you think this bug has been closed incorrectly, please reopen or ask that it be reopened.