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

fusl/include/mqueue.h

+#ifndef _MQUEUE_H
+#define _MQUEUE_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <features.h>
+
+#define __NEED_size_t
+#define __NEED_ssize_t
+#define __NEED_pthread_attr_t
+#define __NEED_time_t
+#define __NEED_struct_timespec
+#include <bits/alltypes.h>
+
+typedef int mqd_t;
+struct mq_attr {
+        long mq_flags, mq_maxmsg, mq_msgsize, mq_curmsgs, __unused[4];
+};
+struct sigevent;
+
+int mq_close(mqd_t);
+int mq_getattr(mqd_t, struct mq_attr *);
+int mq_notify(mqd_t, const struct sigevent *);
+mqd_t mq_open(const char *, int, ...);
+ssize_t mq_receive(mqd_t, char *, size_t, unsigned *);
+int mq_send(mqd_t, const char *, size_t, unsigned);
+int mq_setattr(mqd_t, const struct mq_attr *__restrict, struct mq_attr *__restrict);
+ssize_t mq_timedreceive(mqd_t, char *__restrict, size_t, unsigned *__restrict, const struct timespec *__restrict);
+int mq_timedsend(mqd_t, const char *, size_t, unsigned, const struct timespec *);
+int mq_unlink(const char *);
+
+#ifdef __cplusplus
+}
+#endif
+#endif