Tflint Config Flag Forms

Fixed --config= being ignored by the tflint hook

The built-in tflint hook reads the configuration file out of the arguments you give it, then uses that path for tflint init and for the lint run. It only recognized the space-separated --config <path> spelling, so a hook written as:

before_hook "tflint" {
  commands = ["plan"]
  execute  = ["tflint", "--config=custom.tflint.hcl"]
}

was treated as though no configuration file had been named at all. Terragrunt searched the unit directory and its parents for a .tflint.hcl file instead, and either failed with a config-not-found error or ran tflint init against whatever unrelated configuration the search turned up. Terragrunt now recognizes --config <path>, --config=<path>, -c <path>, and -c=<path>.

The hook also builds --var arguments from the unit's inputs and from TF_VAR_ entries in extra_arguments blocks. Those arguments came out in a different order on every run, which made the logged command line, and anything comparing it between runs, needlessly unstable. They are now ordered by variable name.