runtime/internal/clite/syscall: fix init

[visualfc]

fix #1120

• runtime/internal/clite/syscall: fix init for ErrExist...
• runtime/internal/clite/os: fix stat for macOS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.35%. Comparing base (9a16fff) to head (c8fb7ea).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1122   +/-   ##
=======================================
  Coverage   87.35%   87.35%           
=======================================
  Files          29       29           
  Lines        7228     7228           
=======================================
  Hits         6314     6314           
  Misses        849      849           
  Partials       65       65           

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