build image without systemd

Not only does nixos not have a split systemd.lib package, it also gets
two copies of systemd in the image:
NixOS/nixpkgs#97051
NixOS/nixpkgs#98094

Let's not include it for now, the only detraction is that the
systemd/journald logger wont be available in uwsgi.

On the good side, the image went from 50MB to 30MB now.

.github/workflows/release.yml

@@ -14,9 +14,9 @@ jobs:
 
     - uses: cachix/install-nix-action@v10
       with:
-        nix_path: nixpkgs=https://github.com/gdamjan/nixpkgs/archive/fix-uwsgi-php-try3.tar.gz
+        nix_path: nixpkgs=https://github.com/gdamjan/nixpkgs/archive/my-20.09.tar.gz
 
-    - run: nix-build
+    - run: nix-build --arg withSystemd false
 
     - name: Prepare release files
       run: |