overlays: add zig

hosts/europa/default.nix

@@ -204,6 +204,7 @@ in {
     unzip
     virt-manager
     yt-dlp
+    zig
   ];
 
   system.stateVersion = "21.11";

overlays/default.nix

@@ -2,6 +2,32 @@
 
 {
   nixpkgs.overlays = if isUnstable then [
+    (self: super: {
+      zig = super.zig.overrideAttrs (old: {
+        version = "0.10.0-dev.35e0ff7";
+        src = super.fetchFromGitHub {
+          owner = "ziglang";
+          repo = "zig";
+          rev = "35e0ff7c364487152d786347cf70f47b2a390f12";
+          hash = "sha256-S6m0TrE+Ecm9yBJHgTZRMcKr0W0SoSZYX2CB+5gUSAY=";
+        };
+
+        patches = [ ];
+
+        nativeBuildInputs = with pkgs; [ cmake llvmPackages_14.llvm.dev ];
+
+        buildInputs = with pkgs;
+          [ libxml2 zlib ] ++ (with llvmPackages_14; [ libclang lld llvm ]);
+
+        checkPhase = ''
+          runHook preCheck
+          ls -lart
+          ./zig2 test --cache-dir "$TMPDIR" -I $src/test $src/test/behavior.zig
+          runHook postCheck
+        '';
+      });
+    })
+
     # https://github.com/NixOS/nixpkgs/pull/186130
     (self: super: {
       tidal-hifi = super.tidal-hifi.overrideAttrs (old: {