lixPackageSets.nix-fast-build: init

This adds nix-fast-build to the lixPackageSets scope, allowing the use
of nix-fast-build with Lix and its version of nix-eval-jobs

pkgs/tools/package-management/lix/default.nix

@@ -12,6 +12,7 @@
   ncurses,
   stdenv,
   clangStdenv,
+  nix-fast-build,
 
   storeDir ? "/nix/store",
   stateDir ? "/nix/var",
@@ -85,6 +86,10 @@ let
         nix-eval-jobs = self.callPackage (callPackage ./common-nix-eval-jobs.nix nix-eval-jobs-args) {
           stdenv = lixStdenv;
         };
+
+        nix-fast-build = nix-fast-build.override {
+          inherit (self) nix-eval-jobs;
+        };
       }
     );
 in