Embed crunch in an ELF section rather than static linking

[avsm]

Rather than static linking, we could embed the crunch filesystems in an ELF section. This would:

• speed up compilation time by not passing the block device through ocamlopt
• not require a dynamic block device
• not map the data in memory twice, since it wouldnt be in the code section.

See https://devel.unikernel.org/t/includeos-filesystem-api/108 for the IncludeOS thread on this, so we can obey the same ELF section convention.

[hannesm]

There is now https://github.com/dinosaure/caravan which does this (pending mirage integration).

[hannesm]

As mentioned above, caravan is about that. I tried this for quite some time, it works in some use cases. I don't think it is a good solution (due to issues in respect with reproducible builds): either pass configuration via command line, or block device, or in a git remote. Also, the ELF section is brittle (since size and where memory is mapped is very dependent on solo5 etc.).