refactor: fix Typescript issues in build files

[susnux]

☑️ Resolves

Fixed some small Typescript issues in our build files.

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 2️⃣ Backport to stable8 for maintained Vue 2 version or not applicable

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.20%. Comparing base (49763e7) to head (66c2531).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7922   +/-   ##
=======================================
  Coverage   52.20%   52.20%           
=======================================
  Files         101      101           
  Lines        3174     3174           
  Branches      871      871           
=======================================
  Hits         1657     1657           
  Misses       1271     1271           
  Partials      246      246           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.