by Lwt_unix.wait_read (in read_console, called asynchronously in a fresh task)
and only then convert to a Lwt_io.t (of_fd ~mode:Input) -- thanks to @cfcs
This allows albatross to be run on Linux, where the former code lead to:
- open FIFO
- read <- EOF (although no writer was connected yet)
this works nicely around ocsigen/lwt#741
checks (platform-dependent) all required executables
Vmm_unix.prepare/exec execute solo5-{spt/hvt} depending on the image type
(solo5-elftool figures that out), use jsonm to parse output
Vmm_unix: use ip on linux, no longer ifconfig
