Remove the build container after execution has completed

What does this MR do?

Addresses a regression causing build containers to never be cleaned up

Why was this MR needed?

Unbounded resource utilisation

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

  • Tests
    • All builds are passing
  • Branch has no merge conflicts with master (if you do - rebase it please)

What are the relevant issue numbers?

Closes #2420 (closed)