I forked your repo, added README with STM32F instructions.

[stevemac321]

FYI - I've added steps that add some extra steps that I needed to do from Chapter 2.2 from the book and was able to reproduce on a clean Linux host targetting a STM32F401, I have semihosting working as well. Its big, so I doubt you want to add it, and I've only repeated it once, so if others want to dogfood it and report issues against my repo, cool. However, I'm just bringing it up in case its helpful. Cheers.