Support firmware download using st-util

[master-q]

https://github.com/texane/stlink

1. On terminal A, run "sudo st-util".
2. On terminal B, run "make && make gdbwrite" on project directory.
3. On terminal B, you should see GDB prompt.
4. On terminal B, you can continue STM32Cube application with type "c" on GDB prompt".