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

fusl/src/misc/pty.c

+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <errno.h>
+#include "libc.h"
+#include "syscall.h"
+
+int posix_openpt(int flags)
+{
+        return open("/dev/ptmx", flags);
+}
+
+int grantpt(int fd)
+{
+        return 0;
+}
+
+int unlockpt(int fd)
+{
+        int unlock = 0;
+        return ioctl(fd, TIOCSPTLCK, &unlock);
+}
+
+int __ptsname_r(int fd, char *buf, size_t len)
+{
+        int pty, err;
+        if (!buf) len = 0;
+        if ((err = __syscall(SYS_ioctl, fd, TIOCGPTN, &pty))) return -err;
+        if (snprintf(buf, len, "/dev/pts/%d", pty) >= len) return ERANGE;
+        return 0;
+}
+
+weak_alias(__ptsname_r, ptsname_r);