ci: Make Show test failure summary work with no build dir

[mathbunnyru]

High Level Overview of Change

Working directory is incorrect on Windows, let's try to fix it.
Example: https://github.com/XRPLF/rippled/actions/runs/25677777394/job/75381526818?pr=7109

Context of Change

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.1%. Comparing base (c4c95db) to head (9674b80).

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #7124     +/-   ##
=========================================
- Coverage     82.1%   82.1%   -0.0%     
=========================================
  Files         1010    1010             
  Lines        76064   76064             
  Branches      7380    7375      -5     
=========================================
- Hits         62471   62470      -1     
- Misses       13593   13594      +1     

see 1 file with indirect coverage changes

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