Use writeShellScript

modules/microvm.nix

@@ -165,16 +165,12 @@ in
 
     c3d2.simd.arch = arch-to-host.${config.c3d2.deployment.server};
 
-    system.build = with pkgs; {
-      copyToServer = writeScript "copy-to-${server}" ''
-        #! ${runtimeShell} -e
-
+    system.build = {
+      copyToServer = pkgs.writeShellScript "copy-to-${server}" ''
         nix copy --no-check-sigs --to ssh-ng://root@${serverFQDN} $@
       '';
 
-      runOnServer = writeScript "run-on-${server}" ''
-        #! ${runtimeShell} -e
-
+      runOnServer = pkgs.writeShellScript "run-on-${server}" ''
         ssh root@${serverFQDN} -- $@
       '';
     };