[components/libc/compilers/armlibc]_sys_exit增加RT_WEAK限定,由具体bsp重新实现,通常需要关闭中断,关闭IO输出等

components/libc/compilers/armlibc/stubs.c

@@ -251,7 +251,7 @@ void _ttywrch(int ch)
 #endif
 }
 
-void _sys_exit(int return_code)
+RT_WEAK void _sys_exit(int return_code)
 {
     /* TODO: perhaps exit the thread which is invoking this function */
     while (1);