improve builder skip check: check if its a dir

[tongueroo]

This is a 🐞 bug fix.

• I've added tests (if it's a bug, feature or enhancement)
• I've adjusted the documentation (if it's a feature or enhancement)
• The test suite passes (run bundle exec rspec to verify this)

Summary

Improve the builder skip check. Checks if its a directory by looking for trailing /

Context

Fixes #138

How to Test

Create a module or stack with test_something folder and build it: terraspace build. You should see the files in corresponding the .terraspace-cache folder.

Version Changes

Patch