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

fusl/src/string/strncasecmp.c

+#include <strings.h>
+#include <ctype.h>
+#include "libc.h"
+
+int strncasecmp(const char *_l, const char *_r, size_t n)
+{
+        const unsigned char *l=(void *)_l, *r=(void *)_r;
+        if (!n--) return 0;
+        for (; *l && *r && n && (*l == *r || tolower(*l) == tolower(*r)); l++, r++, n--);
+        return tolower(*l) - tolower(*r);
+}
+
+int __strncasecmp_l(const char *l, const char *r, size_t n, locale_t loc)
+{
+        return strncasecmp(l, r, n);
+}
+
+weak_alias(__strncasecmp_l, strncasecmp_l);