On the core-updates branch, in librsvg, some tests fail on i686 and
armhf.  I've attached a proposed patch, but I haven't yet been able to
test it because I no longer use binary substitutes on my systems and I'm
currently having some difficulties[*] building the base packages.

If someone else would like to test this and push it to core-updates, I'd
be grateful.  It would be sufficient to test on i686, I think.

      Mark

[*] GNU tar's handling of sparse files is broken on btrfs filesystems
    and thus fails its test suite on my system, and the test suite of
    guile-2.2.3 hung up (no output or CPU usage for 30 minutes with a
    defunct guile process) on my x86_64 GuixSD system.