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

fusl/src/termios/tcsetattr.c

Index: fusl/src/termios/tcsetattr.c
diff --git a/fusl/src/termios/tcsetattr.c b/fusl/src/termios/tcsetattr.c
new file mode 100644
index 0000000000000000000000000000000000000000..94df18f91e1718b034303c32b8ee919808ac9f9c
--- /dev/null
+++ b/fusl/src/termios/tcsetattr.c
@@ -0,0 +1,12 @@
+#include <termios.h>
+#include <sys/ioctl.h>
+#include <errno.h>
+
+int tcsetattr(int fd, int act, const struct termios *tio)
+{
+	if (act < 0 || act > 2) {
+		errno = EINVAL;
+		return -1;
+	}
+	return ioctl(fd, TCSETS+act, tio);
+}