cargo rriscv32imac/cargo rrv32imac: Use the riscv32imac-unknown-none-elf targetcargo rriscv32imc/cargo rrv32imc: Use the riscv32imc-unknown-none-elf targetcargo rthumbv7em/cargo rtv7em: Use the thumbv7em-none-eabi targetBefore flashing, write your board name to the environment variable PLATFORM or to a file named platform