clean: remove gcov post-build from nix, for now

default.nix

@@ -37,11 +37,6 @@ let
       mesonBuildType = "debug";
       hardeningDisable = [ "all" ];
       dontStrip = true;
-      # Keep files generated by GCOV, so depending jobs can use them.
-      postInstall = pkgs.lib.optionalString doCoverage ''
-        mkdir -p $out/gcno
-        cp batsched.p/*.gcno $out/gcno/
-      '';
     });
 
     # Batmen integration tests.