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_bsd.go

@@ -1,18 +0,0 @@
-// +build darwin freebsd openbsd netbsd dragonfly
-// +build !appengine
-
-package isatty
-
-import (
-	"syscall"
-	"unsafe"
-)
-
-const ioctlReadTermios = syscall.TIOCGETA
-
-// IsTerminal return true if the file descriptor is terminal.
-func IsTerminal(fd uintptr) bool {
-	var termios syscall.Termios
-	_, _, err := syscall.Syscall6(syscall.SYS_IOCTL, fd, ioctlReadTermios, uintptr(unsafe.Pointer(&termios)), 0, 0, 0)
-	return err == 0
-}