unix: use runtime.KeepAlive in Solaris IoctlSetTermio

This ensures that value remains live for the duration of the ioctl system call.
This pattern is used in all other IoctlSet* functions but appears to have been
forgotten here.

Change-Id: I2b26a5c4e7c862f779427b839327b36c1bc78c82
Reviewed-on: https://go-review.googlesource.com/c/sys/+/259637
Trust: Matt Layher <mdlayher@gmail.com>
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/syscall_solaris.go

@@ -13,6 +13,7 @@
 package unix
 
 import (
+	"runtime"
 	"syscall"
 	"unsafe"
 )
@@ -554,7 +555,9 @@ func Minor(dev uint64) uint32 {
 //sys	ioctl(fd int, req uint, arg uintptr) (err error)
 
 func IoctlSetTermio(fd int, req uint, value *Termio) (err error) {
-	return ioctl(fd, req, uintptr(unsafe.Pointer(value)))
+	err := ioctl(fd, req, uintptr(unsafe.Pointer(value)))
+	runtime.KeepAlive(value)
+	return err
 }
 
 func IoctlGetTermio(fd int, req uint) (*Termio, error) {