Comment 9 for bug 1675138

ok, that doesn't explain why it can't be unversioned.

Then I noticed that it depends on the library package instead of the -dev package (i.e. it's not explicitly pulling in the package containing the relevant .so file), so it seems even more broken to me.

Really that should be 'libboost-filesystem-dev, libboost-system-dev' and nothing else, IMHO.
I'll prepare a bzr MR, given that the mir teams seems to be working with those, and I do not think the mir team would appreciate a direct upload.