xdelta-3.0.11 has a configure option for lzma, and looking at upstream still seems to be present for 3.1.0 (The Github repo at least). It's not available in the ebuild, which makes me have to write something like >=xdelta-3.0 && <xdelta-3.1 or [lzma(+)] without knowing whether it works or not. A lot is saved by having the xdelta-3.1.0 currently masked though.
Given the package is practically dead, it's quite possible that I'll be removing 3.1.0 instead. That said, I don't think xdelta3 makes much sense without LZMA support.
(In reply to Michał Górny from comment #1) > > That said, I don't think xdelta3 makes much sense without LZMA support. I'm up for that as well. Note that currently app-emulation/lxd depends on >=dev-util/xdelta-3.0[lzma(+)] if you want to enable it conditionally, so that shouldn't break either.
Removed 3.1.0.