Destroy the utility thread pool

guix-data-service/jobs/load-new-guix-revision.scm

@@ -2853,16 +2853,17 @@ WHERE builder != 'builtin:download'
                                  extra-inferior-environment-variables
                                  ignore-systems ignore-targets
                                  inferior-memory-limit)
-  (define call-with-utility-thread
-    (let* ((thread-pool
+  (define utility-thread-pool
     (make-fixed-size-thread-pool parallelism))
-           (queued-channel
+  (define call-with-utility-thread
+    (let ((queued-channel
            ;; There might be high demand for this, so order the requests
+           ;; TODO This doesn't shut down
            (spawn-queueing-fiber
-             (fixed-size-thread-pool-channel thread-pool))))
+            (fixed-size-thread-pool-channel utility-thread-pool))))
       (lambda (thunk)
         (call-with-thread
-         thread-pool
+         utility-thread-pool
          thunk
          #:channel queued-channel))))
 
@@ -2965,6 +2966,8 @@ WHERE builder != 'builtin:download'
                   (fibers-force guix-revision-id-promise)))
              (destroy-parallelism-limiter
               read-derivations/parallelism-limiter)
+             (destroy-thread-pool
+              utility-thread-pool)
 
              (and
               (if (defined? 'channel-news-for-commit