Both `--kaniko-dir` and `KANIKO_DIR` needs to be set about kaniko HOT 2 OPEN

When I set --kaniko-dir=foo, during kaniko execution, it still used the config.KanikoDir to get the environment variables(KANIKO_DIR), hance the problem in this issue.

// pkg/executor/build.go:807
dstDir := filepath.Join(config.KanikoDir, strconv.Itoa(index))

When add the --kaniko-dir parameter with corba, the default value is constants.DefaultKanikoPath. I think can remove config.KanikoDir and use the opts.KanikoDir instead.
Because the Kaniko_DIR environment variable and the --kaniko-dir parameter tend to be confusing, don't you think?

// cmd/executor/cmd/root.go:243
RootCmd.PersistentFlags().StringVarP(&opts.KanikoDir, "kaniko-dir", "", constants.DefaultKanikoPath, "Path to the kaniko directory, this takes precedence over the KANIKO_DIR environment variable.")

from kaniko.

when doing copy and snapshooting we called config.KanikoDir which read from envar default from package config
and we are not passing opts.KanikoDir to executeCommand so kaniko options is actually not passing to every command

if err := command.ExecuteCommand(&s.cf.Config, s.args); err != nil {
	return errors.Wrap(err, "failed to execute command")
}

there is no kaniko-dir passsed

fixing all possibilities and pass the opts to every command in executeCommand method will be confusing and make a lot of changes so instead of passing forcing env KANIKO_DIR to values in --kaniko-dir would be better faster and more clear that KANIKO_DIR will be replaced once there is --kaniko-dir flag

with this you no need to specify both of them again to make it work

from kaniko.