Ability to use -chdir=DIR with tf validate and tf fmt

**Describe the solution you'd like**
I need to be able to set the dir via the global terraform argument `-chdir=...` before running validate:

```yaml
repos:
- repo: https://github.com/gruntwork-io/pre-commit
rev: v0.1.23
hooks:
- id: terraform-validate
args: [-chdir=whatever]
```

However, what the above configuration actually does is attempt to pass `-chidr=whatever` to the validate subcommand. In other words, it executes this:

```shell
terraform validate -chdir=whatever
```

But that's an error because `-chdir` is not a valid argument for `terraform validate`.

What I need is a way to execute this:

```shell
terraform -chdir=whatever validate
```

**Describe alternatives you've considered**
I haven't found a way to set the working directory via some other means.