Bug#1017053: fenics-dolfinx: FTBFS on mips64el

[Drew Parsons]

Source: fenics-dolfinx
Followup-For: Bug #1017053

For what it's worth the same error warning from tensor/xtl also shows
up in xtensor's own tests on amd64.

Not clear why it gives dolfinx a problem only on mips64el. I'd expect
the problem to be the same on all arches.

Any any case, I think the work-around is to treat this error warning
as a warning not an error, which is what xtensor itself does.