Describe what this PR does

This change simplifies the code to conditionally set shell variables in the make targets run and test that was introduced in #134

Provide some context for the reviewer

No change in behavior is introduced, just a cleanup of the implementation that should make no difference to the user.

Is there anything that requires special attention

Do you have any questions?

no.

Is the change backward compatible?

should be.

Are there concerns around backward compatibility?

no.

Provide any external context for the change, if any.

none

no future concerns.

Checklist:

[ ] Commit Message Formatting: Commit titles and messages follow guidelines in the developer guide.
[ ] Reviewed the developer guide on Submitting a Pull Request
[ ] Pending release notes updated with breaking and/or notable changes for the next major release.
[ ] Documentation has been updated, if necessary.
[ ] Unit tests have been added, if necessary.
[ ] Integration tests have been added, if necessary.