Update build tools blog post

[chshersh]

After summoner-2.0 and LTS snapshot with GHC-8.8

• [ ] Mention ghcup:
  • https://qfpl.io/posts/multiple-ghcs-ghcup/
• [ ] Mention chocolatey instructions on Windows:
  • https://hub.zhox.com/posts/introducing-haskell-dev/
• [ ] Remove new-* prefix
• [ ] Use ghc-8 by default and a newer LTS snapshot
• [ ] Write more about Nix

Anything else?