realpath.c: fix obsolete syntax warning

[native-api]

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fixes "warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23"

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Summary by cubic

Update realpath_builtin in src/realpath.c to use a standard C prototype instead of K&R syntax. Removes the “function definition without a prototype” warning and keeps builds compatible with C23, with no behavior change.

^{Written for commit bf43036. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}