Bug#942022: librsvg: FTBFS on ppc64el: assertion failed: bounds.x1 >= bounds.x0

[Olivier Tilloy]

Note that ubuntu focal (current development version) has rustc 1.38,
and librsvg 2.44.15 fails to build from source with it. The upstream
project committed a fix to the 2.44 branch
(https://gitlab.gnome.org/GNOME/librsvg/commit/de26c4d8), but they
advise packaging 2.46 instead as 2.44 is EOL.