Add system nix configuration to git build container

nixos-modules/qois/git-ci-runner/default.nix

@@ -91,9 +91,10 @@ with lib;
           emptypassword='$6$1ero.LwbisiU.h3D$GGmnmECbPotJoPQ5eoSTD6tTjKnSWZcjHoVTkxFLZP17W9hRi/XkmCiAMOfWruUwy8gMjINrBMNODc7cYEo4K.'
           useradd --prefix $(pwd) -p "$emptypassword" -m -d /tmp -u "$userid" -g "$groupid" -G nixuser nixuser
 
-          cat <<NIX_CONFIG > etc/nix/nix.conf
+          cp -a ${config.environment.etc."nix/nix.conf".source} etc/nix/nix.conf
+
+          cat <<NIX_CONFIG >> etc/nix/nix.conf
           accept-flake-config = true
-          experimental-features = nix-command flakes
           NIX_CONFIG
 
           cat <<NSSWITCH > etc/nsswitch.conf