Include subprojects in release tarball
Without mocklibc included in the tarball, the build fails if automatic downloads of subprojects are disabled (as they are likely to be in distro build systems):
[...]
Program msginit found: YES (/usr/bin/msginit)
Program msgmerge found: YES (/usr/bin/msgmerge)
Program xgettext found: YES (/usr/bin/xgettext)
Program check-format.sh found: YES (/var/tmp/portage/sys-apps/accountsservice-23.11.69/work/accountsservice-23.11.69/tests/check-format.sh)
tests/meson.build:3:0: ERROR: Automatic wrap-based subproject downloading is disabled
Meson docs about including subprojects in the release tarball: https://mesonbuild.com/Creating-releases.html#include-subprojects-in-your-release