Bug#980809: rmatrix: breaks autopkgtest of r-cran-glmmtmb on s390x

[Graham Inggs]

glmmTMB upstream came up with a minimal reproducer (see forwarded bug):

stopifnot(require("testthat"),
          require("glmmTMB"),
          require("lme4"))
data("Orthodont", package="nlme")
fm1 <- glmmTMB(distance ~ age + (age|Subject), data = Orthodont)

I can confirm this fails on the s390x porterbox using our packages
from unstable.

Is it possible to try this using packages from R / CRAN?