Fix error related to directory does not exist

[Jdubrick]

Please specify the area for this PR
Bug fix

What does does this PR do / why we need it:
This PR adds a check to make sure that before performing a cd command we verify that $stackDir is a directory and not a file. Previous to this check it was attempting to perform cd OWNERS where OWNERS is a file, subsequently throwing an error/warning during the build process.

Which issue(s) this PR fixes:
fixes devfile/api#1207

PR acceptance criteria:

• Test Coverage
  • Are your changes sufficiently tested, and are any applicable test cases added or updated to cover your changes?

Documentation (WIP)

• Does the REST API doc need to be updated with your changes?
• Does the registry library doc need to be updated with your changes?

How to test changes / Special notes to the reviewer:
While trying to test the changes for this fix I was running into issues with running the build.sh script locally. I opened a spike issue to investigate if anything can be changed for this. devfile/api#1447

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (35722ec) 35.58% compared to head (db35460) 35.58%.
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #198   +/-   ##
=======================================
  Coverage   35.58%   35.58%           
=======================================
  Files           7        7           
  Lines        1360     1360           
=======================================
  Hits          484      484           
  Misses        829      829           
  Partials       47       47           

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[michael-valdron]

/lgtm

Confirmed that the build runs locally on amd64 with both test and community registries, error no longer shows up with these changes.

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Jdubrick, michael-valdron

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