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

fusl/src/misc/openpty.c

Index: fusl/src/misc/openpty.c
diff --git a/fusl/src/misc/openpty.c b/fusl/src/misc/openpty.c
new file mode 100644
index 0000000000000000000000000000000000000000..c10740606111778c16b1d6c3dd3adb5a791240b6
--- /dev/null
+++ b/fusl/src/misc/openpty.c
@@ -0,0 +1,40 @@
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <pty.h>
+#include <stdio.h>
+#include <pthread.h>
+
+/* Nonstandard, but vastly superior to the standard functions */
+
+int openpty(int *pm, int *ps, char *name, const struct termios *tio, const struct winsize *ws)
+{
+	int m, s, n=0, cs;
+	char buf[20];
+
+	m = open("/dev/ptmx", O_RDWR|O_NOCTTY);
+	if (m < 0) return -1;
+
+	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+
+	if (ioctl(m, TIOCSPTLCK, &n) || ioctl (m, TIOCGPTN, &n))
+		goto fail;
+
+	if (!name) name = buf;
+	snprintf(name, sizeof buf, "/dev/pts/%d", n);
+	if ((s = open(name, O_RDWR|O_NOCTTY)) < 0)
+		goto fail;
+
+	if (tio) tcsetattr(s, TCSANOW, tio);
+	if (ws) ioctl(s, TIOCSWINSZ, ws);
+
+	*pm = m;
+	*ps = s;
+
+	pthread_setcancelstate(cs, 0);
+	return 0;
+fail:
+	close(m);
+	pthread_setcancelstate(cs, 0);
+	return -1;
+}