Trace addition to nix-support/private

overlay.nix

@@ -23,12 +23,13 @@ let
             if args ? meta && args.meta ? license then builtins.any checkLicense licenses else false;
         in
         if hasUnfreeLicense then
+          builtins.traceVerbose "adding nix-support/private to ${originalDrv.name or originalDrv.pname}" (
           originalDrv.overrideAttrs (old: {
             postInstall = (old.postInstall or "") + ''
               mkdir -p $out/nix-support
               touch $out/nix-support/private
             '';
-          })
+          }))
         else
           originalDrv;
     };