Support mainExe in sub folder on windows

[caesay]

Fixes: #761

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.78%. Comparing base (f389d4e) to head (34e8078).
⚠️ Report is 4 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #817      +/-   ##
===========================================
+ Coverage    43.41%   43.78%   +0.36%     
===========================================
  Files          259      259              
  Lines        20227    20333     +106     
  Branches      2184     2189       +5     
===========================================
+ Hits          8781     8902     +121     
+ Misses       11055    11040      -15     
  Partials       391      391              

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