WIP use hadrian to build ghc

[hamishmack]

Replaces #1460

[hamishmack]

bors try

[iohk-bors[bot]]

try

Build failed:

• buildkite/haskell-dot-nix

[sternenseemann]

I've started working on porting GHC HEAD in nixpkgs to hadrian (https://github.com/NixOS/nixpkgs/pull/179184), maybe that helps you – though I believe our expressions have diverged quite a bit. Haven't gotten very far yet, next up is looking into non-x86_64-linux and cross compilers.

Edit: The work has been merged, but we only build GHC HEAD. Additionally a lot of desireable things don't work yet (like cross) which will require some work (or waiting for upstream fixes): https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/compilers/ghc/common-hadrian.nix

[peterbecich]

Closes https://github.com/input-output-hk/haskell.nix/issues/1595

[hamishmack]

bors try

[iohk-bors[bot]]

try

Timed out.

[hamishmack]

bors try

[iohk-bors[bot]]

try

Timed out.

[hamishmack]

bors try

[iohk-bors[bot]]

try

Timed out.

[hamishmack]

bors try

[hamishmack]

bors try-

[hamishmack]

bors try

[angerman]

bors is dead :( I hope it's back soon.