fix(wc): keep WASI default locale UTF-8 compatible

WASI does not provide an ambient locale, so treating a missing LC_CTYPE/LANG as C/POSIX makes wc -m count bytes by default. Preserve the existing UTF-8 behavior for WASI while keeping POSIX fallback on platforms with native locale environments.

Author: naoNao89

src/uucore/src/lib/features/i18n/charmap.rs

@@ -41,11 +41,15 @@ fn get_effective_ctype_locale() -> Option<String> {
 
 /// Return whether the effective `LC_CTYPE` locale is the byte-oriented C/POSIX locale.
 ///
-/// A missing effective locale defaults to POSIX behavior. Only exact `C` and
-/// `POSIX` locale values are treated as explicit C/POSIX locales; locales such
-/// as `C.UTF-8` are not.
+/// A missing effective locale defaults to POSIX behavior on platforms with a
+/// native locale environment. WASI has no ambient locale, so its default stays
+/// UTF-8-compatible.
 pub fn is_effective_ctype_c_or_posix() -> bool {
-    get_effective_ctype_locale().is_none_or(|locale| locale == "C" || locale == "POSIX")
+    match get_effective_ctype_locale().as_deref() {
+        Some("C" | "POSIX") => true,
+        Some(_) => false,
+        None => cfg!(not(target_os = "wasi")),
+    }
 }
 
 fn get_encoding() -> &'static MbEncoding {