Ignore removed workspace folders in setup-symlinks helper

[c0d1ngm0nk3y]

Summary

It contains 2 fixes:

• The symlinks for workspaces created by setup-symlink had an invalid target.
• If a workspace does not exist, the helper failed because the symlink could not be read.

Use Cases

In case you do not want your final image to contain a workspace and delete it after build, the helper setup-symlinks would fail. Now, instead of failing, this symlink is just not created.

Checklist

• I have viewed, signed, and submitted the Contributor License Agreement.
• I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• I have added an integration test, if necessary.
• I have reviewed the styleguide for guidance on my code quality.
• I'm happy with the commit history on this PR (I have rebased/squashed as needed).

[thitch97]

Hi @c0d1ngm0nk3y, we've done some work that's now on main to fix the tests in this PR. If you could rebase this branch w those changes I'd be happy to get it merged.

[pbusko]

Hi @c0d1ngm0nk3y, we've done some work that's now on main to fix the tests in this PR. If you could rebase this branch w those changes I'd be happy to get it merged.

The PR has been rebased