fix[tool]: fix cross-compilation issues, add windows CI

[charles-cooper]

What I did

How I did it

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Commit message

this commit fixes some `InputBundle` bugs on windows due to how
path-manipulation operations are implemented. it also fixes compilation
of cross-OS archives by settling on using posix paths as standard (this
follows the ZIP archive spec, and is explicit in the python stdlib
implementation of zipfile).

this commit also enables a windows job in the CI for tests, to prevent
bugs like these in the future and increase cross-OS coverage.

references:
- https://stackoverflow.com/a/8177003
- https://hg.python.org/cpython/file/2.7/Lib/zipfile.py#l295
- https://hg.python.org/cpython/file/2.7/Lib/zipfile.py#l1046

Description for the changelog

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 8.33333% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 50.29%. Comparing base (c276c94) to head (1afe87b).

❗ Current head 1afe87b differs from pull request most recent head a43d2e8. Consider uploading reports for the commit a43d2e8 to get more accurate results

Files	Patch %	Lines
vyper/compiler/output_bundle.py	0.00%	7 Missing ⚠️
vyper/cli/vyper_json.py	0.00%	2 Missing ⚠️
vyper/compiler/input_bundle.py	33.33%	2 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4014       +/-   ##
===========================================
- Coverage   90.95%   50.29%   -40.67%     
===========================================
  Files         106      106               
  Lines       15280    15282        +2     
  Branches     3365     3365               
===========================================
- Hits        13898     7686     -6212     
- Misses        946     6965     +6019     
- Partials      436      631      +195     

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[pcaversaccio]

tested locally and it finally worked 😄