Use IoctlSetPointerInt from golang.org/x/sys/unix

Update the golang.org/x/sys/unix dependency and use unix.IoctlSetPointerInt
instead of manually implementing it. This fixes the build on darwin
where direct syscalls, i.e.  unix.Syscall(SYS_IOCTL, ...) are no longer
allowed and exported as of golang/sys@6fcdbc0

go.mod

@@ -4,5 +4,5 @@ go 1.13
 
 require (
 	github.com/pkg/errors v0.8.1
-	golang.org/x/sys v0.0.0-20191120155948-bd437916bb0e
+	golang.org/x/sys v0.0.0-20200916030750-2334cc1a136f
 )

go.sum

@@ -1,4 +1,4 @@
 github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
-golang.org/x/sys v0.0.0-20191120155948-bd437916bb0e h1:N7DeIrjYszNmSW409R3frPPwglRwMkXSBzwVbkOjLLA=
-golang.org/x/sys v0.0.0-20191120155948-bd437916bb0e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200916030750-2334cc1a136f h1:6Sc1XOXTulBN6imkqo6XoAXDEzoQ4/ro6xy7Vn8+rOM=
+golang.org/x/sys v0.0.0-20200916030750-2334cc1a136f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

tc_darwin.go

@@ -19,7 +19,6 @@ package console
 import (
 	"fmt"
 	"os"
-	"unsafe"
 
 	"golang.org/x/sys/unix"
 )
@@ -29,18 +28,10 @@ const (
 	cmdTcSet = unix.TIOCSETA
 )
 
-func ioctl(fd, flag, data uintptr) error {
-	if _, _, err := unix.Syscall(unix.SYS_IOCTL, fd, flag, data); err != 0 {
-		return err
-	}
-	return nil
-}
-
 // unlockpt unlocks the slave pseudoterminal device corresponding to the master pseudoterminal referred to by f.
 // unlockpt should be called before opening the slave side of a pty.
 func unlockpt(f *os.File) error {
-	var u int32
-	return ioctl(f.Fd(), unix.TIOCPTYUNLK, uintptr(unsafe.Pointer(&u)))
+	return unix.IoctlSetPointerInt(int(f.Fd()), unix.TIOCPTYUNLK, 0)
 }
 
 // ptsname retrieves the name of the first available pts for the given master.