Update Nix infrastructure

The Nix infrastructure of the current project is broken and does not
compile. Rather than fixing it, I rewrote it entirely using nix flakes
instead.

Author: jaschutte

default.nix

@@ -0,0 +1,50 @@
+{ 
+  description = "A flake for developing & using circuit-notation";
+  inputs = {
+    clash-compiler.url = "github:clash-lang/clash-compiler";
+  };
+  outputs = { self, flake-utils, clash-compiler, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        # What version of the GHC compiler to use
+        compiler-version = "ghc910";
+
+        pkgs = (import clash-compiler.inputs.nixpkgs {
+          inherit system;
+        }).extend clash-compiler.overlays.${compiler-version};
+        clash-pkgs = pkgs."clashPackages-${compiler-version}";
+
+        overlay = final: prev: clash-pkgs // {
+          circuit-notation = prev.developPackage {
+            root = ./.;
+            overrides = overlay;
+          };
+        };
+
+        hs-pkgs = pkgs."clashPackages-${compiler-version}".extend overlay;
+      in
+      {
+        # Expose the set of haskell packages used to build circuit-notation, so that dependants can
+        # use the same set of packages
+        hs-pkgs.${compiler-version} = hs-pkgs;
+
+        devShells.default = hs-pkgs.shellFor {
+          packages = p: [
+            p.circuit-notation
+          ];
+
+          nativeBuildInputs = 
+            [
+              # Haskell stuff
+              hs-pkgs.cabal-install
+              hs-pkgs.cabal-plan
+              hs-pkgs.haskell-language-server
+              hs-pkgs.fourmolu
+            ]
+          ;
+        };
+        packages = {
+          default = hs-pkgs.circuit-notation;
+        };
+      });
+}