Fix build duration display.

* src/cuirass/templates.scm (build-details): Fix build duration display.

src/cuirass/templates.scm

@@ -291,11 +291,17 @@ system whose names start with " (code "guile-") ":" (br)
       (tr (th "Name")
           (td ,(assq-ref build #:nix-name)))
       (tr (th "Duration")
-          (td ,(or (and-let* ((start (assq-ref build #:starttime))
-                              (stop  (assq-ref build #:stoptime)))
-                     (string-append (number->string (- stop start))
-                                    " seconds"))
-                   "—")))
+          (td ,(let ((timestamp (time-second (current-time time-utc)))
+                     (start (assq-ref build #:starttime))
+                     (stop  (assq-ref build #:stoptime)))
+                 (cond
+                  ((and (> start 0) (> stop 0))
+                   (string-append (number->string (- stop start))
+                                  " seconds"))
+                  ((> start 0)
+                   (string-append (number->string (- timestamp start))
+                                  " seconds"))
+                  (else "—")))))
       (tr (th "Finished")
           (td ,(if completed?
                    (time->string (assq-ref build #:stoptime))