Consume buildHaskell functions

Use the newly defined `buildHaskell` function for a few of my existing Haskell
projects. So far, it works as intended!

scratch/brilliant/default.nix

@@ -1,26 +1,16 @@
 let
-  pkgs = import (builtins.fetchGit {
-    url = "https://github.com/NixOS/nixpkgs-channels";
-    ref = "nixos-20.03";
-    rev = "afa9ca61924f05aacfe495a7ad0fd84709d236cc";
-  }) {};
-
-  ghc = pkgs.haskellPackages.ghcWithPackages (hpkgs: with hpkgs; [
-    optparse-applicative
-    unordered-containers
-    split
-  ]);
-in pkgs.stdenv.mkDerivation {
+  briefcase = import /home/wpcarro/briefcase {};
+in briefcase.buildHaskell.program {
   name = "transform-keyboard";
-  buildInputs = [];
-  src = builtins.path {
+  srcs = builtins.path {
     path = ./.;
     name = "transform-keyboard-src";
   };
-  buildPhase = ''
-    ${ghc}/bin/ghc ./Main.hs
-  '';
-  installPhase = ''
-    mkdir -p $out && mv Main $out/transform-keyboard
-  '';
+  deps = hpkgs: with hpkgs; [
+    optparse-applicative
+    unordered-containers
+    split
+    rio
+  ];
+  ghcExtensions = [];
 }