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

fusl/src/thread/sem_post.c

Index: fusl/src/thread/sem_post.c
diff --git a/fusl/src/thread/sem_post.c b/fusl/src/thread/sem_post.c
new file mode 100644
index 0000000000000000000000000000000000000000..31e3293d20504a85deaebca70ded98567ba9561e
--- /dev/null
+++ b/fusl/src/thread/sem_post.c
@@ -0,0 +1,17 @@
+#include <semaphore.h>
+#include "pthread_impl.h"
+
+int sem_post(sem_t *sem)
+{
+	int val, waiters, priv = sem->__val[2];
+	do {
+		val = sem->__val[0];
+		waiters = sem->__val[1];
+		if (val == SEM_VALUE_MAX) {
+			errno = EOVERFLOW;
+			return -1;
+		}
+	} while (a_cas(sem->__val, val, val+1+(val<0)) != val);
+	if (val<0 || waiters) __wake(sem->__val, 1, priv);
+	return 0;
+}