Install fails on Bullseye: undefined HOME variable

[alexAubin]

Since Bullseye, install via CLI doesnt include a HOME variable anymore.

This is to make it easier to spot issues that would only be triggered on webadmin : app scripts should not assume that HOME is defined

[...]
71986 WARNING       from mautrix_signal.get_version import git_tag, git_revision, version, linkified_version
71987 WARNING     File "/tmp/pip-req-build-65c059fm/mautrix_signal/get_version.py", line 9, in <module>
71987 WARNING       "HOME": os.environ["HOME"],
71988 WARNING     File "/usr/lib/python3.9/os.py", line 679, in __getitem__
71988 WARNING       raise KeyError(key) from None
71989 WARNING   KeyError: 'HOME'

The fix should be to export HOME with an appropriate value during install/...