builder: fix assertion error

[hijackthe2]

Fix assertion error by explicitly specifying type when building nydus in macos arm64 environment.

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Details

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Types of changes

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

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• I have updated the documentation accordingly.
• I have added tests to cover my changes.

[codecov]

Codecov Report

Merging #1471 (16545dd) into master (89882a4) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1471      +/-   ##
==========================================
- Coverage   54.85%   54.85%   -0.01%     
==========================================
  Files         123      123              
  Lines       40477    40477              
  Branches    40477    40477              
==========================================
- Hits        22205    22204       -1     
- Misses      17033    17034       +1     
  Partials     1239     1239              

Files	Coverage Δ
builder/src/stargz.rs	74.67% <100.00%> (ø)

... and 2 files with indirect coverage changes