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

fusl/src/stdio/funlockfile.c

Index: fusl/src/stdio/funlockfile.c
diff --git a/fusl/src/stdio/funlockfile.c b/fusl/src/stdio/funlockfile.c
new file mode 100644
index 0000000000000000000000000000000000000000..30a07ef4b37433d46ec5ef44e9c67001a5841e7e
--- /dev/null
+++ b/fusl/src/stdio/funlockfile.c
@@ -0,0 +1,15 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+void __unlist_locked_file(FILE *);
+
+void funlockfile(FILE *f)
+{
+	if (f->lockcount == 1) {
+		__unlist_locked_file(f);
+		f->lockcount = 0;
+		__unlockfile(f);
+	} else {
+		f->lockcount--;
+	}
+}