Update Makefile

[znicholls]

Description

Update the Makefile so we only set COV_DIR when we need it, not every time we use the Makefile

Checklist

Please confirm that this pull request has done the following:

• Tests added
• Documentation added (where applicable)
• Changelog item added to changelog/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (9f03851) to head (6b8f226).
⚠️ Report is 143 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #17   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines           18        18           
=========================================
  Hits            18        18           

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[znicholls]

@mzecc a super trivial one. I'm going to merge to just keep things moving. Shout out if you have any questions