Fix local build

[pleshakov]

Proposed changes

Problem:

c52b4da renamed the local build folder.
However, the renaming in the Dockerfile wasn't done so the local building of NKG using local go env become broken.

Solution:
Fix the Dockerfile

Tests:
Manually run make container

Note: needs #888 for successfull testing

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork