Modify CubeMX resulting RT-Thread makefile project

Modify CubeMX resulting RT-Thread makefile project

Using RT-Thread official based CubeMX transplanted RT-Thread Nano generated Makefile engineering errors at compile time, simply change it.

1. Add context_gcc.sfiles. We need to add in the Makefile this .s file, you can find it in CubeMX generated by the project, if you find a file called capital expansion .S please change it to lowercase .s, in case the compilation is not the same .

   # ASM sources
   ASM_SOURCES =  \
   startup_stm32f103xb.s \
   Middlewares/Third_Party/RealThread_RTOS_RT-Thread/libcpu/arm/cortex-m3/context_gcc.s
   

2. Modify the startup file (modify startup_stm32f103xb.s), will bl mainbe changed bl entry.

   /* Call the application's entry point.*/
   bl entry
   bx lr
   .size Reset_Handler, .-Reset_Handler
   

End modify the compiler should be no problem, but there may be a warning that I am here obj defined but not used, do not ignore it