msvc: Append the default .pdb extension for the /Fd argument

[ikolomiko]

MSVC appends the .pdb extension for the file path given for the /Fd argument, if the extension is omitted. This commit adds this functionality for feature parity.

Fixes #2620

[codecov-commenter]

Codecov Report

❌ Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.82%. Comparing base (146f4df) to head (922500d).

Files with missing lines	Patch %	Lines
src/compiler/msvc.rs	76.92%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2621      +/-   ##
==========================================
- Coverage   72.82%   72.82%   -0.01%     
==========================================
  Files          68       68              
  Lines       37114    37120       +6     
==========================================
+ Hits        27029    27031       +2     
- Misses      10085    10089       +4     

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[codspeed-hq]

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 2 skipped benchmarks¹

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_{Comparing ikolomiko:main (922500d) with main (146f4df)}

Footnotes

1. 2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[AJIOB]

@ikolomiko, please, recheck the format: looks like it's failed

[ikolomiko]

Oopsies, fixed it