Bug#990547: libsystemd-shared broken in Multi-Arch

[dann frazier]

Source: systemd
Version: 247.3-5

I noticed that systemd-machined was failing to start on an arm64
box. This box had armhf enabled, and turns out systemd had been
cross-graded over to systemd:armhf[*]. It still had
systemd-container:arm64 installed, so now I had an arm64
/lib/systemd/systemd-machine, but an armhf
/lib/systemd/libsystemd-shared-244.so.

libsystemd-shared-244.so is from the systemd package. Since systemd is
marked Multi-Arch: foreign, systemd:armhf was able to incorrectly
satisfy systemd-container:arm64's dependency on systemd.

[*] kudos to Multi-Arch that I simply hadn't noticed