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

fusl/src/stdio/swprintf.c

Index: fusl/src/stdio/swprintf.c
diff --git a/fusl/src/stdio/swprintf.c b/fusl/src/stdio/swprintf.c
new file mode 100644
index 0000000000000000000000000000000000000000..f75eb112e7c0d7e22b79c03204cc00c6af7575e7
--- /dev/null
+++ b/fusl/src/stdio/swprintf.c
@@ -0,0 +1,13 @@
+#include <stdarg.h>
+#include <wchar.h>
+
+int swprintf(wchar_t *restrict s, size_t n, const wchar_t *restrict fmt, ...)
+{
+	int ret;
+	va_list ap;
+	va_start(ap, fmt);
+	ret = vswprintf(s, n, fmt, ap);
+	va_end(ap);
+	return ret;
+}
+