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

fusl/src/stdio/fputwc.c

Index: fusl/src/stdio/fputwc.c
diff --git a/fusl/src/stdio/fputwc.c b/fusl/src/stdio/fputwc.c
new file mode 100644
index 0000000000000000000000000000000000000000..789fe9c90e98e72faccb570f373bb0ef8f5c384d
--- /dev/null
+++ b/fusl/src/stdio/fputwc.c
@@ -0,0 +1,40 @@
+#include "stdio_impl.h"
+#include "locale_impl.h"
+#include <wchar.h>
+#include <limits.h>
+#include <ctype.h>
+
+wint_t __fputwc_unlocked(wchar_t c, FILE *f)
+{
+	char mbc[MB_LEN_MAX];
+	int l;
+	locale_t *ploc = &CURRENT_LOCALE, loc = *ploc;
+
+	if (f->mode <= 0) fwide(f, 1);
+	*ploc = f->locale;
+
+	if (isascii(c)) {
+		c = putc_unlocked(c, f);
+	} else if (f->wpos + MB_LEN_MAX < f->wend) {
+		l = wctomb((void *)f->wpos, c);
+		if (l < 0) c = WEOF;
+		else f->wpos += l;
+	} else {
+		l = wctomb(mbc, c);
+		if (l < 0 || __fwritex((void *)mbc, l, f) < l) c = WEOF;
+	}
+	if (c==WEOF) f->flags |= F_ERR;
+	*ploc = loc;
+	return c;
+}
+
+wint_t fputwc(wchar_t c, FILE *f)
+{
+	FLOCK(f);
+	c = __fputwc_unlocked(c, f);
+	FUNLOCK(f);
+	return c;
+}
+
+weak_alias(__fputwc_unlocked, fputwc_unlocked);
+weak_alias(__fputwc_unlocked, putwc_unlocked);