Upgrade to GHC 9.4

[supermario]

This work was prompted by the new discovery of various crashes in the current macos-arm64 build which used GHC 9.0.2 (which also required the use of llvm@12).

Building with GHC 9.4 appears to have resolved the issue with the need for llvm, however due to the Word8 changes (donated by @robinheghan with thanks to his work on Gren), @lydell discovered a regression in the following code that worked previously but no longer does:

module Main exposing (main)

import Html

åäö = "test"

main = Html.text åäö

Once we resolve this bug we should be able to cut a new macos-arm64 release into the @lydell/elm npm package after wider testing confirms it's working okay on M* macs.

Todo

• Figure out Word8 API change regression bug
  • https://github.com/gren-lang/compiler/pull/227/files
• Restore fixed version bounds in elm.cabal once sorted
• Test new binaries widely

[lydell]

FYI I tested applying the (at the time, 3) commits of this branch that aren’t in master onto elm/compiler@c9aefb6 which is the release commit of https://github.com/elm/compiler/releases/tag/0.19.1! It went well!

Good to know once we’re ready to compile a new macOS ARM binary for @lydell/elm and elm-tooling.

[supermario]

Regression appears to be fixed now, with thanks to @robinheghan , @jxxcarlson , @avh4 and @lydell for repro & investigation 🙌