To use this use `sudo systemctl edit fwupd.service` and set
`Environment="FWUPD_SYSFSFWDIR=/usr/share/installed-tests/fwupd"`
Fixes https://github.com/fwupd/fwupd/issues/3441
The fact that it currently lives in uefi-capsule is a historical
accident, and it doesn't really belong to tpm-eventlog either.
Fixes some of https://github.com/fwupd/fwupd/issues/3901