Developers need to apply workaround in order to build Tails during the release process

Once the new tag is pushed, building from another branch fails, because "Not building from a tag, but last version in changelog was released".

That's a sanity check to avoid building a release using time-based snapshots. We could:

• move this sanity check to the release process
• in that situation, instead of failing the build: ignore the tag and use time-based snapshots