Add a "fork" of musl as //fusl.

fusl/src/stdio/fgetws.c

+#include "stdio_impl.h"
+#include <wchar.h>
+
+wint_t __fgetwc_unlocked(FILE *);
+
+wchar_t *fgetws(wchar_t *restrict s, int n, FILE *restrict f)
+{
+        wchar_t *p = s;
+
+        if (!n--) return s;
+
+        FLOCK(f);
+
+        for (; n; n--) {
+                wint_t c = __fgetwc_unlocked(f);
+                if (c == WEOF) break;
+                *p++ = c;
+                if (c == '\n') break;
+        }
+        *p = 0;
+        if (ferror(f)) p = s;
+
+        FUNLOCK(f);
+
+        return (p == s) ? NULL : s;
+}
+
+weak_alias(fgetws, fgetws_unlocked);