We've had josh in here previously, but it was kind of immature back
then. The repository looks much better now and I'd like to give it
another try.
Josh is a Rust project, the build here is done with naersk.
Change-Id: I3731340d00ce1eb4cef55de114e1915579e47ef3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3017
Reviewed-by: lukegb <lukegb@tvl.fyi>
Tested-by: BuildkiteCI
