fix(gerrit): make buildbot able to read the priv ssh key

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

nix/coordinator.nix

@@ -209,7 +209,7 @@ in
               "${cfg.gerrit.domain}",
               "${cfg.gerrit.username}",
               "${toString cfg.gerrit.port}",
-              "${cfg.gerrit.privateKeyFile}",
+              read_secret_file('buildbot-service-private-key'),
               projects=${builtins.toJSON cfg.gerrit.projects},
               allowed_origins=${builtins.toJSON cfg.allowedOrigins},
               url=${builtins.toJSON config.services.buildbot-master.buildbotUrl},
@@ -269,6 +269,7 @@ in
         LoadCredential = [
           "buildbot-nix-workers:${cfg.workersFile}"
           "buildbot-oauth2-secret:${cfg.oauth2.clientSecretFile}"
+          "buildbot-service-private-key:${cfg.gerrit.privateKeyFile}"
         ];
       };
     };