Fix build on Solaris/illumos.

Fill in the missing ioctlReadTermios/ioctlWriteTermios, and switch to
syscall.Syscall as Syscall6 is not available.  Probably makes this work
on AIX too as a bonus.

terminal/runereader_posix.go

@@ -44,7 +44,7 @@ func (rr *RuneReader) Buffer() *bytes.Buffer {
 
 // For reading runes we just want to disable echo.
 func (rr *RuneReader) SetTermMode() error {
-	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(rr.stdio.In.Fd()), ioctlReadTermios, uintptr(unsafe.Pointer(&rr.state.term)), 0, 0, 0); err != 0 {
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(rr.stdio.In.Fd()), ioctlReadTermios, uintptr(unsafe.Pointer(&rr.state.term))); err != 0 {
 		return err
 	}
 
@@ -56,15 +56,15 @@ func (rr *RuneReader) SetTermMode() error {
 	newState.Cc[syscall.VMIN] = 1
 	newState.Cc[syscall.VTIME] = 0
 
-	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(rr.stdio.In.Fd()), ioctlWriteTermios, uintptr(unsafe.Pointer(&newState)), 0, 0, 0); err != 0 {
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(rr.stdio.In.Fd()), ioctlWriteTermios, uintptr(unsafe.Pointer(&newState))); err != 0 {
 		return err
 	}
 
 	return nil
 }
 
 func (rr *RuneReader) RestoreTermMode() error {
-	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(rr.stdio.In.Fd()), ioctlWriteTermios, uintptr(unsafe.Pointer(&rr.state.term)), 0, 0, 0); err != 0 {
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(rr.stdio.In.Fd()), ioctlWriteTermios, uintptr(unsafe.Pointer(&rr.state.term))); err != 0 {
 		return err
 	}
 	return nil

terminal/runereader_unix.go

@@ -0,0 +1,14 @@
+// copied from golang.org/x/term/term_unix_other.go
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build aix || solaris || zos
+// +build aix solaris zos
+
+package terminal
+
+import "golang.org/x/sys/unix"
+
+const ioctlReadTermios = unix.TCGETS
+const ioctlWriteTermios = unix.TCSETS