Switch to ZST for tarball

It is faster then Gzip and available in MEEP FPGA cluster.

.gitlab-ci.yml

@@ -17,7 +17,7 @@ build:lagarto-ox-tarball:
     - out=/ceph/home/gitlab-runner/public_html/nixos-riscv/
     - fn=$(ls | head -1)
     - cp $fn $out/$fn
-    - rm -f $out/latest.tar.gz
-    - ln -s $out/$fn $out/latest.tar.gz
+    - rm -f $out/latest.tar.zst
+    - ln -s $out/$fn $out/latest.tar.zst
     - cd ..
     - rm result

lagarto-ox.nix

@@ -625,10 +625,10 @@
 
       installPhase = ''
         mkdir -p $out
-        tar czvf $out/${COMMIT}.tar.gz nixos-riscv
+        tar -I zstd -cvf $out/${COMMIT}.tar.zst nixos-riscv
       '';
 
-      nativeBuildInputs = with final.buildPackages; [ rsync ];
+      nativeBuildInputs = with final.buildPackages; [ rsync zstd ];
     };
 
     opensbi = prev.opensbi.overrideAttrs (old: rec {