chore(linux): Fix launchpad script

- We have to provide env variable to be able to select correct
  dependencies at build time
- Add focal and groovy and remove xenial and eoan
- We need to build once before creating the source package so that
  the man pages get generated. In v14 we do that during the binary
  build, but that requires additional build dependencies, so for v13
  we do it this way.