Bootstrap dev with Rust on Particle Xenon / Argon / Boron

1. 2nd gen debugger
2. probe-run
3. flip-link
4. thumbv7em-none-eabihf

1. connect debugger to xenon, insert to usb
2. export DEFMT_LOG=info (to see output from main.rs)
3. cargo run --example hello

1. Scaffold future projects with https://github.com/knurling-rs/app-template
2. the debugger was not initially found by probe-run --list-probes
   • holding in the button while inserting it and it worked
   • after that even it works without holding button

• https://github.com/knurling-rs
• https://github.com/daschl/nrf52840dk-sample
• https://github.com/nrf-rs/nrf-hal

• https://ferrous-systems.com/blog/defmt-rtt-linker-error/