FIX osu build - always declare function os_setting_update()

[yrichard-ledger]

Description

Depending on the target or the on compiler version used, osu build can fail on an implicit declaration of os_setting_update(). That's because this function is declared behind HAVE_LANGUAGE_PACK flag.

This PR moves the function declaration to fix this issue

Changes include

• [ *] Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e54fb1b) 69.09% compared to head (e205812) 69.09%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #462   +/-   ##
=======================================
  Coverage   69.09%   69.09%           
=======================================
  Files          11       11           
  Lines         877      877           
=======================================
  Hits          606      606           
  Misses        271      271           

Flag	Coverage Δ
unittests	69.09% <ø> (ø)

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