Reintroduce support for iadd carry variants and isub borrow variants for RISC ISAs which had been removed in https://github.com/CraneStation/cranelift/pull/961 and https://github.com/CraneStation/cranelift/pull/962 because of the lack of a proper flags register in RISC architectures.
This crate contains the metaprogram used by cranelift-codegen. It's not useful on its own.