Invalid time zone specified: posix/... breaks steam settings on batocera flatpak

[Planet of the]

steam settings and the interface menu just show the error box on batocera with the flatpak, big picture system menu too.

/usr/share/zoneinfo/Asia on batocera is a symlink to posix/Asia, so readlink -f /etc/localtime ends up at zoneinfo/posix/Asia/Shanghai and steamwebhelper takes that whole path bit as the zone name

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Invalid time zone specified: posix/Asia/Shanghai

flatpak override --env=TZ doesnt change anything. a v44 box throws the same thing with posix/America/Vancouver so it isnt only old builds