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

fusl/src/termios/cfsetospeed.c

Index: fusl/src/termios/cfsetospeed.c
diff --git a/fusl/src/termios/cfsetospeed.c b/fusl/src/termios/cfsetospeed.c
new file mode 100644
index 0000000000000000000000000000000000000000..80c790f1fda1b2046a8746d6b4e2b436ab95ac0c
--- /dev/null
+++ b/fusl/src/termios/cfsetospeed.c
@@ -0,0 +1,22 @@
+#include <termios.h>
+#include <sys/ioctl.h>
+#include <errno.h>
+#include "libc.h"
+
+int cfsetospeed(struct termios *tio, speed_t speed)
+{
+	if (speed & ~CBAUD) {
+		errno = EINVAL;
+		return -1;
+	}
+	tio->c_cflag &= ~CBAUD;
+	tio->c_cflag |= speed;
+	return 0;
+}
+
+int cfsetispeed(struct termios *tio, speed_t speed)
+{
+	return speed ? cfsetospeed(tio, speed) : 0;
+}
+
+weak_alias(cfsetospeed, cfsetspeed);