pkgs/top-level/make-tarball.nix: just don't do, like, most of it

- Making sure everything evals? That's covered by release-checks!
- Building a list of tarballs? We throw it out anyway!
- Copying files around to produce the right paths in the tarball? Just tell tar to do it!

Also, multithread xz compression for additional fast.

Tarball job is under two minutes now. I hate computers.

pkgs/top-level/make-tarball.nix

@@ -1,7 +1,3 @@
-/* Hydra job to build a tarball for Nixpkgs from a Git checkout.  It
-   also builds the documentation and tests whether the Nix expressions
-   evaluate correctly. */
-
 { nixpkgs
 , officialRelease
 , pkgs ? import nixpkgs.outPath {}
@@ -31,54 +27,32 @@ pkgs.releaseTools.sourceTarball {
     echo "git-revision is $(cat .git-revision)"
   '';
 
-  requiredSystemFeatures = [ "big-parallel" ]; # 1 thread but ~36G RAM (!) see #227945
-
   dontBuild = false;
 
   doCheck = true;
 
   checkPhase = ''
-    set -o pipefail
-
-    export NIX_STATE_DIR=$TMPDIR
-    export NIX_PATH=nixpkgs=$TMPDIR/barf.nix
-    opts=(--option build-users-group "")
-    nix-store --init
-
-    echo "checking eval-release.nix"
-    nix-instantiate --eval --strict --show-trace ./maintainers/scripts/eval-release.nix > /dev/null
-
-    echo "checking find-tarballs.nix"
-    nix-instantiate --readonly-mode --eval --strict --show-trace --json \
-       ./maintainers/scripts/find-tarballs.nix \
-      --arg expr 'import ./maintainers/scripts/all-tarballs.nix' > $TMPDIR/tarballs.json
-    nrUrls=$(jq -r '.[].url' < $TMPDIR/tarballs.json | wc -l)
-    echo "found $nrUrls URLs"
-    if [ "$nrUrls" -lt 10000 ]; then
-      echo "suspiciously low number of URLs"
-      exit 1
-    fi
-
     echo "generating packages.json"
-    mkdir -p $out/nix-support
-    echo -n '{"version":2,"packages":' > tmp
-    nix-env -f . -I nixpkgs=$src -qa --meta --json --show-trace --arg config 'import ${./packages-config.nix}' "''${opts[@]}" >> tmp
-    echo -n '}' >> tmp
-    packages=$out/packages.json.br
-    < tmp sed "s|$(pwd)/||g" | jq -c | brotli -9 > $packages
-    rm tmp
 
+    packages=$out/packages.json.br
+
+    (
+      echo -n '{"version":2,"packages":'
+      NIX_STATE_DIR=$TMPDIR NIX_PATH= nix-env -f $src -qa --meta --json --show-trace --arg config 'import ${./packages-config.nix}'
+      echo -n '}'
+    ) | sed "s|$src/||g" | jq -c | brotli -9 > $packages
+
+    mkdir -p $out/nix-support
     echo "file json-br $packages" >> $out/nix-support/hydra-build-products
   '';
 
   distPhase = ''
     mkdir -p $out/tarballs
-    mkdir ../$releaseName
+    XZ_OPT="-T0" tar \
-    cp -prd . ../$releaseName
+      --transform="s/^[.]/$releaseName/" \
-    (cd .. && tar cfa $out/tarballs/$releaseName.tar.xz $releaseName) || false
+      --create \
+      --xz \
+      --file=$out/tarballs/$releaseName.tar.xz \
+      .
   '';
-
-  meta = {
-    maintainers = [ ];
-  };
 }