gnu: apr-util: Run 'make check' sequentially.

* gnu/packages/apr.scm (apr-util)[arguments]: Add #:parallel-tests?.

gnu/packages/apr.scm

@@ -85,7 +85,13 @@ around or take advantage of platform-specific deficiencies or features.")
              (system* "./configure"
                       (string-append "--prefix=" out)
                       (string-append "--with-apr=" apr)))))
-        %standard-phases)))
+        %standard-phases)
+
+       ;; There are race conditions during 'make check'.  Typically, the
+       ;; 'testall' executable is not built yet by the time 'make check' tries
+       ;; to run it.  See
+       ;; <http://lists.gnu.org/archive/html/guix-devel/2014-03/msg00261.html>.
+       #:parallel-tests? #f))
     (home-page "http://apr.apache.org/")
     (synopsis "One of the Apache Portable Runtime Library companions")
     (description