nixos/github-runner: start Runner.Listener directly in ExecStart=

The `runsvc.sh` script wraps a JavaScript script which starts
`Runner.Listener` and also handles failures. This has the downside that
the service _always_ exits with status code 0, i.e., success. This
causes frequent service restarts when running in ephemeral mode with a
faulty config as Systemd always sees a success exit status. To prevent
this, this commit changes the service config to call `Runner.Listener`
directly. The JavaScript wrapper stops the process with a SIGINT, hence,
the Systemd unit now sends a SIGINT to stop the service.

nixos/modules/services/continuous-integration/github-runner.nix

@@ -173,7 +173,7 @@ in
       ] ++ cfg.extraPackages;
 
       serviceConfig = rec {
-        ExecStart = "${cfg.package}/bin/runsvc.sh";
+        ExecStart = "${cfg.package}/bin/Runner.Listener run --startuptype service";
 
         # Does the following, sequentially:
         # - If the module configuration or the token has changed, purge the state directory,
@@ -314,8 +314,7 @@ in
         # By default, use a dynamically allocated user
         DynamicUser = true;
 
-        KillMode = "process";
-        KillSignal = "SIGTERM";
+        KillSignal = "SIGINT";
 
         # Hardening (may overlap with DynamicUser=)
         # The following options are only for optimizing: