[submitters] Export PROD_MOUNT variable if it exists

[cbentejac]

Description

This PR exports the PROD_MOUNT environment variable along PROD and PROD_ROOT if it exists.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (develop@e54eadd). Learn more about missing BASE report.
⚠️ Report is 2 commits behind head on develop.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #2923   +/-   ##
==========================================
  Coverage           ?   80.78%           
==========================================
  Files              ?       56           
  Lines              ?     7749           
  Branches           ?        0           
==========================================
  Hits               ?     6260           
  Misses             ?     1489           
  Partials           ?        0           

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

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.