vars: add generators.<name>.finalScript

nixosModules/clanCore/vars/generator.nix

@@ -0,0 +1,36 @@
+{
+  lib,
+  config,
+  pkgs,
+  ...
+}:
+{
+  finalScript = lib.mkOptionDefault ''
+    set -eu -o pipefail
+
+    export PATH="${lib.makeBinPath config.path}:${pkgs.coreutils}/bin"
+
+    ${lib.optionalString (pkgs.stdenv.hostPlatform.isLinux) ''
+      # prepare sandbox user on platforms where this is supported
+      mkdir -p /etc
+
+      cat > /etc/group <<EOF
+      root:x:0:
+      nixbld:!:$(id -g):
+      nogroup:x:65534:
+      EOF
+
+      cat > /etc/passwd <<EOF
+      root:x:0:0:Nix build user:/build:/noshell
+      nixbld:x:$(id -u):$(id -g):Nix build user:/build:/noshell
+      nobody:x:65534:65534:Nobody:/:/noshell
+      EOF
+
+      cat > /etc/hosts <<EOF
+      127.0.0.1 localhost
+      ::1 localhost
+      EOF
+    ''}
+    ${config.script}
+  '';
+}