Fixes to build against Solo5 targets

[mato]

These changes fix the build with MODE=ukvm and MODE=virtio.

@yomimono Could you please check I'm doing the right thing in 9073886 and not papering over a dependency problem in the mirage frontend for the Solo5 targets. (See also #177)

[mato]

Regarding the io-page dependency, for kv_ro, shouldn't this be pulled in by https://github.com/mirage/mirage/blob/master/lib/mirage.ml#L174? For some reason that's not happening, hence #177.

[yomimono]

I think your suspicion about papering over a dependency problem in the mirage frontend for solo5 is warranted; mirage configure should really be figuring out that you want crunch, and that crunch needs io-page. I happened to be looking at #177 yesterday and got to the same point as your comment, but not further; I'll dig a bit deeper today. io-page has gotten preferential treatment in the xen case in the past, but I'm not sure whether that behavior is preserved in the Functoria version of Mirage.

[yomimono]

mirage/mirage#585 for some investigation and a proposed fix for kv_ro; it definitely should be fixed in mirage instead of here.

[yomimono]

@mato, want to force-push without the last commit? I just merged the fix for io-page's dependencies in mirage, so it shouldn't be needed anymore.

[mato]

@yomimono Re-pushed, I still need eaf4394 to get the io_page example to build, I think there's no way around that. (Tried mucking with adding default_io_page in there but couldn't get the types right...)

[Drup]

Where does the dependency comes from ?

[mato]

@Drup The io-page example uses Io_page directly: https://github.com/mirage/mirage-skeleton/blob/master/io_page/unikernel.ml#L3

[Drup]

Ah, then it's fine to manually add it.