version: update the generation to something closer to what we had previously
We still have a regression compared to what we had in 6.9, but as far as I understand some code would be need to be written to be able to customize the postX
section according to the branch.
This only affect people install custom build from multiple branches, which is rare. So I don't think the remaining limitation to be a release blocker.
(cc @paugier as he is the one doing most of the packaging changes)