Docbuilder fails if package requests newer build-tool

[andreasabel]

https://hackage.haskell.org/package/helf-1.0.20240318/reports/2

Configuring helf-1.0.20240318...
Error: cabal-3.10.2.1: The program 'alex' version >=3.4.0.0 && <4 is required
but the version found at /home/builder/.cabal/bin/alex is version 3.2.7.1

We should deploy to hackage the fixed cabal-install:

• https://github.com/haskell/cabal/issues/9756

Or maybe the problem is that build-tools do no not get built:

• https://github.com/haskell/hackage-server/issues/821