make terraform/validate does not to run on Terraform v0.12.X

[Gowiem]

Describe the Bug

Running make terraform/validate on Terraform v0.12.X prints the following message:

Terraform 0.12 does not support validate without skipping variables

Expected Behavior

I would expect the terraform/validate target to not care about this skipping variables flag as it doesn't seem needed, but maybe I am missing something.

Steps to Reproduce

1. git clone https://github.com/cloudposse/terraform-aws-ssm-parameter-store
2. make
3. make terraform/install TERRAFORM_VERSION=0.12.24
4. make terraform/validate
5. Notice that Terraform validate is not run and the target prints "Terraform 0.12 does not support validate without skipping variables".

Environment (please complete the following information):

• Build Harness Version: master
• OS: MacOSX
• Version: 10.15.4

Additional Context

• When I run tf validate locally without the Makefile / Build-harness -- I get the expected, useful output:

Error: Missing required argument

The argument "region" is required, but was not set.

[Nuru]

Terraform v0.12 support is no longer a priority. Even if it were, simply supplying region is not enough to get all our modules to pass, and we require that they pass before releasing them.