Rust should now build natively on Solaris. A couple of us Oracle folks have pushed a number of fixes, so it should just work now, at least on nightly (well, beta now, I guess). I haven't yet tried an unpatched 1.16, so I'm not sure about that. And there's a fix to the fs2 crate that I still need to figure out the best solution, but if you get stuck on
flock(), let me know and I'll send you a patch.
Note that I haven't yet tried Solaris 11, only S12, so there may be more fixes required, but I can't think of any reason why it shouldn't just work.