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

fusl/src/thread/pthread_mutex_lock.c

Index: fusl/src/thread/pthread_mutex_lock.c
diff --git a/fusl/src/thread/pthread_mutex_lock.c b/fusl/src/thread/pthread_mutex_lock.c
new file mode 100644
index 0000000000000000000000000000000000000000..d0c93cab50119feee0741b14006f346f000b87c6
--- /dev/null
+++ b/fusl/src/thread/pthread_mutex_lock.c
@@ -0,0 +1,14 @@
+#include "pthread_impl.h"
+
+int __pthread_mutex_timedlock(pthread_mutex_t *restrict, const struct timespec *restrict);
+
+int __pthread_mutex_lock(pthread_mutex_t *m)
+{
+	if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL
+	    && !a_cas(&m->_m_lock, 0, EBUSY))
+		return 0;
+
+	return __pthread_mutex_timedlock(m, 0);
+}
+
+weak_alias(__pthread_mutex_lock, pthread_mutex_lock);