let qtPrepareTool give right path for app_bundle

Change-Id: Ieb4979244d741c9d9d0c11a035c18ced87ea28f5
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>

mkspecs/features/qt_functions.prf

@@ -180,7 +180,13 @@ defineTest(qtPrepareTool) {
         } else {
             $$1 = $$eval($$1).exe
         }
+    } else:contains(QMAKE_HOST.os, Darwin) {
+        BUNDLENAME = $$eval($$1).app/Contents/MacOS/$$2
+        exists($$BUNDLENAME) {
+            $$1 = $$BUNDLENAME
         }
+    }
+
     export($$1)
 }