Solve the problem of undefined reference to `__aeabi_unwind_cpp_pr0' - ARM bare metal learning

1. Encounter a problem: when compiling the code, it prompts an undefined error message undefined reference to `__aeabi_unwind_cpp_pr0

Second, the solution: 

    1. Add -nostdlib in the makefile, that is, do not use the standard library

    

    2. Execute make clean to delete the files generated by the previous compilation  

    3. Execute make to recompile the project

    

    After successful compilation, a *.bin file is generated, which can be burned into the embedded development board for testing