gnu: webkitgtk: Remove unnecessary make flag.

* gnu/packages/webkit.scm (webkitgtk): Remove make-flags.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/packages/webkit.scm

@@ -62,8 +62,7 @@ (define-public webkitgtk
                           "-DPORT=GTK"
                           (string-append ; uses lib64 by default
                            "-DLIB_INSTALL_DIR="
-                           (assoc-ref %outputs "out") "/lib"))
-       #:make-flags '("lib=lib"))) ; uses lib64 by default
+                           (assoc-ref %outputs "out") "/lib"))))
     (native-inputs
      `(("bison" ,bison)
        ("gettext" ,gnu-gettext)