Cranelift code generation comes to Rust

Other Rust code generation backends include the GCC one, which is nearing some kind of usable status and hopes to become installable via rustup within the next months (https://blog.antoyo.xyz/rustc_codegen_gcc-progress-report-31), as well as an extremely experimental one to compile using Microsoft's .Net framework (since apparently .Net bytecode is also capable of representing unsafe operations).