Add MacOS support for typescript model build script

[Jdubrick]

What does this PR do?

This PR adds support for recognizing if the user running the script is on MacOS. Due to the fact that some commands work differently if they are on freeBSD (Mac) or GNU/Linux.

The changes include:

1. Detecting what OS a user is on and grabbing the directory path appropriately. realpath is used for Darwin and readlink -m is used for everything else.
2. Using the detected OS it alters the sed command to ensure it works for all users.

Which issue(s) does this PR fix

fixes #1380

PR acceptance criteria

Testing and documentation do not need to be complete in order for this PR to be approved. We just need to ensure tracking issues are opened.

• Open new test/doc issues under the devfile/api repo
• Check each criteria if:
• There is a separate tracking issue. Add the issue link under the criteria
  or
• test/doc updates are made as part of this PR
• If unchecked, explain why it's not needed

• Unit/Functional tests

• QE Integration test

• Documentation

• Client Impact

How to test changes / Special notes to the reviewer

Try and build the typescript model by running bash ./build/typescript-model/generate.sh from the root of the api repo.

[thepetk]

/lgtm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 35.75%. Comparing base (ee044f7) to head (6b9cfed).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1457   +/-   ##
=======================================
  Coverage   35.75%   35.75%           
=======================================
  Files          52       52           
  Lines        6696     6696           
=======================================
  Hits         2394     2394           
  Misses       4158     4158           
  Partials      144      144           

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[michael-valdron]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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

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