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

fusl/src/linux/clone.c

+#include <stdarg.h>
+#include <unistd.h>
+#include "pthread_impl.h"
+#include "syscall.h"
+
+int clone(int (*func)(void *), void *stack, int flags, void *arg, ...)
+{
+        va_list ap;
+        pid_t *ptid, *ctid;
+        void  *tls;
+
+        va_start(ap, arg);
+        ptid = va_arg(ap, pid_t *);
+        tls  = va_arg(ap, void *);
+        ctid = va_arg(ap, pid_t *);
+        va_end(ap);
+
+        return __syscall_ret(__clone(func, stack, flags, arg, ptid, tls, ctid));
+}