linux: Convert dup2 calls to dup3

Convert syscall.Dup2 calls to syscall.Dup3.  The dup2 syscall is depreciated
and is not available on some architectures.  Fixes build errors like these when
building for arm64:

  console_linux.go: undefined: syscall.Dup2

Signed-off-by: Geoff Levand <[email protected]>

Author: glevand

Diff for: console_linux.go

@@ -92,7 +92,7 @@ func (c *linuxConsole) mount(rootfs, mountLabel string, uid, gid int) error {
 	return syscall.Mount(c.slavePath, dest, "bind", syscall.MS_BIND, "")
 }
 
-// dupStdio opens the slavePath for the console and dup2s the fds to the current
+// dupStdio opens the slavePath for the console and dups the fds to the current
 // processes stdio, fd 0,1,2.
 func (c *linuxConsole) dupStdio() error {
 	slave, err := c.open(syscall.O_RDWR)
@@ -101,7 +101,7 @@ func (c *linuxConsole) dupStdio() error {
 	}
 	fd := int(slave.Fd())
 	for _, i := range []int{0, 1, 2} {
-		if err := syscall.Dup2(fd, i); err != nil {
+		if err := syscall.Dup3(fd, i, 0); err != nil {
 			return err
 		}
 	}

Diff for: rootfs_linux.go

@@ -272,7 +272,7 @@ func reOpenDevNull(rootfs string) error {
 		}
 		if stat.Rdev == devNullStat.Rdev {
 			// Close and re-open the fd.
-			if err := syscall.Dup2(int(file.Fd()), fd); err != nil {
+			if err := syscall.Dup3(int(file.Fd()), fd, 0); err != nil {
 				return err
 			}
 		}