Nice to have explicit instructions to see the Rust code generated from a P4 program

[jafingerhut]

Maybe such instructions are already in this repo somewhere, and I missed them. Happy to be pointed to those, if they exist.

If not, it would be nice to see how one can generate Rust code from a P4 source program, and store the resulting Rust code in a file somewhere.

[jafingerhut]

Answering my own question, as I have found that x4c myprog.p4 by default writes a Rust file out.rs, with command line option to change that output file name. I will consider creating a PR to mention this somewhere in the book text.