On the host side you have to use blash with the rtt option. (At the time of writing it's on a branch, not on main - please use the branch backtrace)
A simple cargo run should flash the binary via blash and show the output.
To see full backtraces you should compile and run like this: cargo run -Z build-std=core --target riscv32imc-unknown-none-elf
Uncomment the relevant parts in main.rs to make the code panic.