Apptainer mount fix for ResStock and OpenStudio 3.8

[nmerket]

Pull Request Description

In ResStock with OpenStudio 3.8 the BuildExistingModel measure is trying to access the buildstock.rb file in the resources directory using a relative path. We weren't mounting that in in apptainer, but just the hpxml-measures subdirectory. This should fix that.

Checklist

Not all may apply

• Code changes (must work)
• Tests exercising your feature/bug fix (check coverage report on Checks -> BuildStockBatch Tests -> Artifacts)
• Coverage has increased or at least not decreased. Update minimum_coverage in .github/workflows/coverage.yml as necessary.
• All other unit and integration tests passing
• Update validation for project config yaml file changes
• Update existing documentation
• Run a small batch run on Kestrel/Eagle to make sure it all works if you made changes that will affect Kestrel/Eagle
• Add to the changelog_dev.rst file and propose migration text in the pull request

[whiphi92]

This change fixed the problem @joseph-robertson and I were running into on Kestrel.

[afontani]

Probably need a test and changelog before moving forward with merging.

[rajeee]

@nmerket Tested it and it works in Kestrel. So, LGTM.