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

fusl/src/multibyte/wctomb.c

Index: fusl/src/multibyte/wctomb.c
diff --git a/fusl/src/multibyte/wctomb.c b/fusl/src/multibyte/wctomb.c
new file mode 100644
index 0000000000000000000000000000000000000000..de7ed84d9bbcfc83d5c8e77a45a1677b8a7ab971
--- /dev/null
+++ b/fusl/src/multibyte/wctomb.c
@@ -0,0 +1,14 @@
+/* 
+ * This code was written by Rich Felker in 2010; no copyright is claimed.
+ * This code is in the public domain. Attribution is appreciated but
+ * unnecessary.
+ */
+
+#include <stdlib.h>
+#include <wchar.h>
+
+int wctomb(char *s, wchar_t wc)
+{
+	if (!s) return 0;
+	return wcrtomb(s, wc, 0);
+}