Without this change, the ChibiOS shell prompt does not show up reliably on
Linux, and possibly other operating systems.
For a detailed walk-through covering the individual problems and causes, see:
https://michael.stapelberg.ch/posts/2021-04-27-linux-usb-virtual-serial-cdc-acm/
I verified that this approach works with:
1. Linux 5.10
2. Windows 10
3. macOS Big Sur on a MacBook Air M1