add qemu-run

[japaric]

this lets us test binfmt end-to-end (encoder + decoder + singleton) on an
emulated microcontroller

To use:

$ cargo install --path qemu-run
$ cd firmware
$ cargo run --bin log
0.000000 INFO Hello!
0.000001 INFO World!
0.000002 INFO The answer is 42
0.000003 INFO S { x: 1, y: 256 }
0.000004 INFO X { y: Y { z: 42 } }

[japaric]

wasn't needed when piping QEMU's output (I guess the usual difference in line buffering between terminal output and process pipes)

[jonas-schievink]

This requires installing qemu-run first, right? You could also use "cargo run --bin qemu-run" instead.

[japaric]

Because this gets invoked within a workspace where the default compilation target is not host that approach requires passing --target $HOST to cargo-run. Hardcoding HOST=Linux means that it won't work on macOS or Windows.

[jonas-schievink]

Ah, right. That's unfortunate.

[jonas-schievink]

We could remove the default target, other than that I don't have any better suggestion. I do think not having to install part of the package can be helpful at times (it ensures that the newest version of qemu-run is automatically built and used), but if you think otherwise we can merge this as-is.

[japaric]

removed the default compilation target, set cargo run as the runner and added some Cargo aliases to avoid typing out the --target flag