version-info.py isn't reliably updated on deployments

When we do a production deployment of Launchpad, version-info.py is generated by the build on carob which runs "rm -f version-info.py; make version-info.py"; but if we deploy something other than the latest commit, then version-info.py isn't updated to match, which means that we end up deploying something that refers to combo URLs for the wrong commit and thus end up with things like broken JavaScript.

Only ever deploying the tip of stable (or at least the latest commit that's been built on carob) avoids this problem, but it would be better to make things a bit more robust here.