[repo] Fix variable usage in test-aot-compatibility script

[eerhardt]

Minor fix up of the powershell script.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.71%. Comparing base (6250307) to head (888a10e).
Report is 239 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5645      +/-   ##
==========================================
+ Coverage   83.38%   85.71%   +2.33%     
==========================================
  Files         297      254      -43     
  Lines       12531    11036    -1495     
==========================================
- Hits        10449     9460     -989     
+ Misses       2082     1576     -506     

Flag	Coverage Δ
unittests	?
unittests-Solution-Experimental	85.70% <ø> (?)
unittests-Solution-Stable	85.46% <ø> (?)
unittests-Unstable-Core	19.95% <ø> (?)

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see 114 files with indirect coverage changes