Manually update buildah to v1.13.1

Should help with #791.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/mattn/go-isatty/isatty_solaris.go

@@ -1,16 +0,0 @@
-// +build solaris
-// +build !appengine
-
-package isatty
-
-import (
-	"golang.org/x/sys/unix"
-)
-
-// IsTerminal returns true if the given file descriptor is a terminal.
-// see: http://src.illumos.org/source/xref/illumos-gate/usr/src/lib/libbc/libc/gen/common/isatty.c
-func IsTerminal(fd uintptr) bool {
-	var termio unix.Termio
-	err := unix.IoctlSetTermio(int(fd), unix.TCGETA, &termio)
-	return err == nil
-}