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

fusl/src/thread/pthread_cond_signal.c

Index: fusl/src/thread/pthread_cond_signal.c
diff --git a/fusl/src/thread/pthread_cond_signal.c b/fusl/src/thread/pthread_cond_signal.c
new file mode 100644
index 0000000000000000000000000000000000000000..119c00abcd9904b46fa7eabbc6093dfb736df276
--- /dev/null
+++ b/fusl/src/thread/pthread_cond_signal.c
@@ -0,0 +1,12 @@
+#include "pthread_impl.h"
+
+int __private_cond_signal(pthread_cond_t *, int);
+
+int pthread_cond_signal(pthread_cond_t *c)
+{
+	if (!c->_c_shared) return __private_cond_signal(c, 1);
+	if (!c->_c_waiters) return 0;
+	a_inc(&c->_c_seq);
+	__wake(&c->_c_seq, 1, 0);
+	return 0;
+}