buildenv: fix version not being set (#359448)

pkgs/build-support/buildenv/default.nix

@@ -77,17 +77,21 @@ let
     (lib.remove null)
   ];
 in runCommand name
-  rec {
+  (rec {
     inherit manifest ignoreCollisions checkCollisionContents passthru
             meta pathsToLink extraPrefix postBuild
-            nativeBuildInputs buildInputs pname version;
+            nativeBuildInputs buildInputs;
     pkgs = builtins.toJSON chosenOutputs;
     extraPathsFrom = lib.optional includeClosures (writeClosure pathsForClosure);
     preferLocalBuild = true;
     allowSubstitutes = false;
     # XXX: The size is somewhat arbitrary
     passAsFile = if builtins.stringLength pkgs >= 128*1024 then [ "pkgs" ] else [ ];
-  }
+  } // lib.optionalAttrs (pname != null) {
+    inherit pname;
+  } // lib.optionalAttrs (version != null) {
+    inherit version;
+  })
   ''
     ${buildPackages.perl}/bin/perl -w ${builder}
     eval "$postBuild"