ch-image build --force: Dockerfile segfaults on Cray XC40

As reported by @scanon, the following Dockerfile fails to build with --force (or without, but that's expected) on an XC40 front-end:

FROM ubuntu
RUN apt-get update && apt-get install -y autoconf automake gcc g++ make gfortran wget curl

(Currently this gets Ubuntu Focal.)

Step 2 of installing fakeroot segfaults:

workarounds: init step 2: $ apt-get update && apt-get install -y pseudo
[...]
The following NEW packages will be installed:
  libpseudo libsqlite3-0 pseudo
0 upgraded, 3 newly installed, 0 to remove and 1 not upgraded.
[...]
Processing triggers for libc-bin (2.31-0ubuntu9.2) ...
Segmentation fault
Segmentation fault
dpkg: error processing package libc-bin (--configure):
 installed libc-bin package post-installation script subprocess returned error exit status 139
Errors were encountered while processing:
 libc-bin
W: chown to root:adm of file /var/log/apt/term.log failed - OpenLog (22: Invalid argument)
E: Sub-process /usr/bin/dpkg returned an error code (1)

The Dockerfile builds fine on my Debian Buster development box.