generic-linux-gpu: put systemd unit in lib/systemd

This is where unit files are expected to be, making GPU setup compatible
with things like selinux. Fixes #8438. The `resources/` directory was
kept because it is expected to be used in the future.

(cherry picked from commit a3ac4bb1f8)

modules/targets/generic-linux/gpu/setup/default.nix

@@ -18,13 +18,14 @@ stdenv.mkDerivation {
   src = ./.;
   patchPhase = ''
     substituteInPlace non-nixos-gpu* \
-      --replace '@@resources@@' "$out/resources" \
-      --replace '@@statedir@@' '${nixStateDirectory}' \
-      --replace '@@env@@' "${nonNixosGpuEnv}"
+      --replace-quiet '@@resources@@' "$out/resources" \
+      --replace-quiet '@@statedir@@' '${nixStateDirectory}' \
+      --replace-quiet '@@systemddir@@' "$out/lib/systemd/system" \
+      --replace-quiet '@@env@@' "${nonNixosGpuEnv}"
   '';
   installPhase = ''
-    mkdir -p $out/{bin,resources}
+    mkdir -p $out/{bin,resources,lib/systemd/system}
     cp non-nixos-gpu-setup $out/bin
-    cp non-nixos-gpu.service $out/resources
+    cp non-nixos-gpu.service $out/lib/systemd/system
   '';
 }

modules/targets/generic-linux/gpu/setup/non-nixos-gpu-setup

@@ -5,7 +5,7 @@ set -e
 # Install the systemd service file and ensure that the store path won't be
 # garbage-collected as long as it's installed.
 unit_path=/etc/systemd/system/non-nixos-gpu.service
-ln -sf @@resources@@/non-nixos-gpu.service "$unit_path"
+ln -sf @@systemddir@@/non-nixos-gpu.service "$unit_path"
 ln -sf "$unit_path" "@@statedir@@"/gcroots/non-nixos-gpu.service
 
 systemctl daemon-reload