refactor[tool]: relax output bundle construction

[charles-cooper]

this always produces a valid input bundle. it doesn't guarantee that paths are always anonymized, but it guarantees that the output bundle is produced, rather than panicking (which is rather frustrating UX).

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[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 92.98%. Comparing base (c1b6130) to head (85d87a6).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
vyper/compiler/output_bundle.py	50.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4706      +/-   ##
==========================================
- Coverage   92.99%   92.98%   -0.01%     
==========================================
  Files         131      131              
  Lines       19094    19096       +2     
  Branches     3324     3325       +1     
==========================================
  Hits        17757    17757              
- Misses        899      900       +1     
- Partials      438      439       +1     

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