Fix the CI

[Larsouille25]

Is your feature request related to a problem? Please describe.
The CI says LLVM isn't installed but there is an action to install it. After an issue opened here, the CI needs to install llvm-config with the according version of LLVM. (for the moment as long as this issue is not closed, the CI will be deactivated)

Describe the solution you'd like
Install, rather compile llvm with https://github.com/llvmenv/llvmenv

Describe alternatives you've considered
Create a github action that compiles LLVM and install it but too long and maybe later I'll do it but now I don't have time.

[Larsouille25]

OR !! I've just found a marvelous CI with Inkwell, they wrote their own action and I think I will (if they agree) copy this because it's amazing

[Larsouille25]

OR with this mun-lang/mun#526

[Larsouille25]

like said in #6 i don't know if it's worth the time to do CI and tests / benchmarks ...