gnu: kleopatra: Allow skipping tests.

* gnu/packages/kde-pim.scm (kleopatra)[arguments]: Have custom 'check
phase honor #:tests?.

gnu/packages/kde-pim.scm

@@ -1017,8 +1017,9 @@ (define-public kleopatra
      `(#:phases
        (modify-phases %standard-phases
          (replace 'check
-           (lambda _
-             (invoke "dbus-launch" "ctest" ".")
+           (lambda* (#:key tests? #:allow-other-keys)
+             (when tests?
+               (invoke "dbus-launch" "ctest" "."))
              #t)))))
     (home-page "https://kde.org/applications/utilities/org.kde.kleopatra")
     (synopsis "Certificate Manager and Unified Crypto GUI")