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

fusl/src/thread/pthread_cond_destroy.c

Index: fusl/src/thread/pthread_cond_destroy.c
diff --git a/fusl/src/thread/pthread_cond_destroy.c b/fusl/src/thread/pthread_cond_destroy.c
new file mode 100644
index 0000000000000000000000000000000000000000..8c5551600e8c35d0a9f5fe194ee060d8303c22f6
--- /dev/null
+++ b/fusl/src/thread/pthread_cond_destroy.c
@@ -0,0 +1,14 @@
+#include "pthread_impl.h"
+
+int pthread_cond_destroy(pthread_cond_t *c)
+{
+	if (c->_c_shared && c->_c_waiters) {
+		int cnt;
+		a_or(&c->_c_waiters, 0x80000000);
+		a_inc(&c->_c_seq);
+		__wake(&c->_c_seq, -1, 0);
+		while ((cnt = c->_c_waiters) & 0x7fffffff)
+			__wait(&c->_c_waiters, 0, cnt, 0);
+	}
+	return 0;
+}