default.nix: Add kore attribute (#2030)

Updating haskell.nix removed `project.kore.components.all`, so we are adding a
virtual package `kore` that combines all the executables.

Author: ttuegel

default.nix

@@ -41,13 +41,19 @@ let
 
   shell = import ./shell.nix { inherit default; };
 
+  version = project.kore.components.exes.kore-exec.version;
+
   default =
     {
       inherit pkgs project;
       cache = [
         project.roots
         (pkgs.haskell-nix.withInputs shell)
       ];
+      kore = pkgs.symlinkJoin {
+        name = "kore-${version}";
+        paths = pkgs.lib.attrValues project.kore.components.exes;
+      };
     };
 
 in default