We have already noted this issue and raised a ticket regarding the same. Thanks for bringing it to our notice and providing a workaround as well.
Another workaround for the same issue is to include the header file wiced_platform.h, inside wiced_rtc_time.c, for STM32F4xx platforms where the typecasting is already done.
Still hit the same compile error in sdk-6.0.0.
It's so strange that even you know how to fix it, you don't fix it in new sdk release.