artiq-board: move inputs outside inner function

artiq-fast/artiq-board.nix

@@ -1,13 +1,11 @@
 # Install Vivado in /opt and add to /etc/nixos/configuration.nix:
 #  nix.sandboxPaths = ["/opt"];
 
-{ pkgs }:
-{ target
-, variant
-, buildCommand ? "python -m artiq.gateware.targets.${target} -V ${variant}"
-, extraInstallCommands ? ""}:
+{ pkgs
+}:
 
 let
+  vivado = builtins.trace "vivado" (import ./vivado.nix { inherit pkgs; });
   artiqSrc = import ./pkgs/artiq-src.nix { fetchgit = pkgs.fetchgit; };
   artiqpkgs = builtins.trace "artiqpkgs" (import ./default.nix { inherit pkgs; });
   fetchcargo = import ./fetchcargo.nix {
@@ -44,8 +42,13 @@ let
       '';
   };
 
-  vivado = builtins.trace "vivado" (import ./vivado.nix { inherit pkgs; });
+in
+{ target
+, variant
+, buildCommand ? "python -m artiq.gateware.targets.${target} -V ${variant}"
+, extraInstallCommands ? ""}:
 
+let
 # Board packages are Python modules so that they get added to the ARTIQ Python
 # environment, and artiq_flash finds them.
 in pkgs.python3Packages.toPythonModule (pkgs.stdenv.mkDerivation rec {