Modernize packaging scripts

[ctlong]

Description

• Adds shebang directive for the default shell (used when the directive is missing).
• Ignore shellcheck warnings related to missing compile.env source files.
• Removes unnecessary GOPATH export.
• Removes -mod=vendor flag from go build command, as that flag is on by default in recent versions of Go.

Type of change

• [x] Maintenance chore
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Testing performed?

• [ ] Unit tests
• [ ] Integration tests
• [ ] Acceptance tests

Checklist:

• [x] This PR is being made against the main branch, or relevant version branch
• [x] I have made corresponding changes to the documentation
• [x] I have added testing for my changes

[ctlong]

⚠️ I have not tested this at all ⚠️