fix: cache the build dir by link

[frostming]

Signed-off-by: Frost Ming me@frostming.com

Pull Request Checklist

• A news fragment is added in news/ describing what is new.
• Test cases added for changed code.

Describe what you have changed in this PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.82%. Comparing base (92dfb19) to head (c66de24).
Report is 75 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3455      +/-   ##
==========================================
+ Coverage   85.57%   85.82%   +0.24%     
==========================================
  Files         112      112              
  Lines       11557    11561       +4     
  Branches     2538     2539       +1     
==========================================
+ Hits         9890     9922      +32     
+ Misses       1136     1107      -29     
- Partials      531      532       +1     

Flag	Coverage Δ
unittests	85.61% <100.00%> (+0.23%)	⬆️

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