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)

tests/modules/targets-linux/generic-linux-gpu/nvidia-enabled.nix

@@ -39,11 +39,12 @@ in
     setupScript="$TESTED/home-path/bin/non-nixos-gpu-setup"
     assertFileExists "$setupScript"
 
-    # Find the resources directory
-    resourcesPath=$(grep -oP '/nix/store/[^/]+-non-nixos-gpu/resources' "$setupScript" | head -1)
+    # Find the service file
+    storePath="$(dirname "$(readlink "''${setupScript}")")"/../
+    servicePath="$storePath/lib/systemd/system/non-nixos-gpu.service"
 
     # Extract the GPU environment path
-    envPath=$(grep -oP '/nix/store/[^/]+-non-nixos-gpu' "$resourcesPath/non-nixos-gpu.service" | head -1)
+    envPath=$(grep -oP '/nix/store/[^/]+-non-nixos-gpu' "$servicePath" | head -1)
 
     if [[ -z "$envPath" ]]; then
       fail "Could not find GPU environment path in service file"

tests/modules/targets-linux/generic-linux-gpu/setup-package-contents.nix

@@ -11,19 +11,22 @@
     assertFileExists "$setupScript"
     assertFileIsExecutable "$setupScript"
 
-    # Find and check the resources directory
-    resourcesPath=$(grep -oP '/nix/store/[^/]+-non-nixos-gpu/resources' "$setupScript" | head -1)
-    assertDirectoryExists "$resourcesPath"
-
     # Check that gcroots dir was set
     cat "$setupScript"
     assertFileRegex "$setupScript" ' "/custom/state/directory"/gcroots'
 
-    serviceFile="$resourcesPath/non-nixos-gpu.service"
-    assertFileExists "$serviceFile"
-
     # Check that no placeholders remain
-    assertFileNotRegex "$serviceFile" '@@[^@]\+@@'
     assertFileNotRegex "$setupScript" '@@[^@]\+@@'
+
+    # Check that expected files are present and free of placeholders
+    storePath="$(dirname "$(readlink "''${setupScript}")")"/../
+    expectedFiles=(
+      lib/systemd/system/non-nixos-gpu.service
+    )
+
+    for f in "''${expectedFiles[@]}"; do
+      assertFileExists "$storePath/$f"
+      assertFileNotRegex "$storePath/$f" '@@[^@]\+@@'
+    done
   '';
 }