* Enforce LC_NUMERIC=C on Posix systems (#16724)
Initialising Qt with native LC_NUMERIC affects XML import on CLI (freecad -c)
This causes sketch constraints and potentially other components relying on numeric constants to break or have incorrect values.
Forcing LC_NUMERIC to C avoids this issue and enforces reproducible behaviour on all locales.
This does not affect the number format displayed in the GUI, as set in preferences.
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