Merge #135 135: cargo: Add support for building OpenTitan apps r=alistair23 a=alistair23 This fixes https://github.com/tock/libtock-rs/issues/134 and adds support for building OT apps, Signed-off-by: Alistair Francis <alistair.francis@wdc.com> Co-authored-by: Alistair Francis <alistair.francis@wdc.com>