Instead of having committed files containing a single developer's serials, use
optional includes to include a local config file for each board.
If you have only a single board connected, simply:
$ make -f Makefile.<board> clean all flash
If you have multiple boards connected, make sure to fill in the appropriate
hla_serial in your openocd.<board>.local.cfg file, and then run the same
commands.
As with F103 generic, there's no readily available L1 board with USB device
A custom LED is used to track boot process, but otherwise this should be
portable to any L1 board, except for the openocd configuration file.
Tests pass straight away, which is good, as it uses the existing f103 usb
driver.
