Link with -ObjC to have ObjC categories working

If we don't link with ObjC, categories as used by Blink will not work
and cause crashes at runtime when failing selectors.

Change-Id: I81520cc46ed996377b86760232bc99e275e48ff3
Reviewed-by: Joerg Bornemann <[email protected]>

Author: carewolf

src/core/qtwebengine.gypi

@@ -108,5 +108,8 @@
           '<(chromium_src_dir)/build/linux/system.gyp:fontconfig',
         ],
       }],
+      ['OS=="mac"', {
+        'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-ObjC']},
+      }],
     ],
 }