fix: `--build.bin` path for windows

[kareemmahlees]

closes #589

Changes

• Path fed to --build.bin is converted to an absolute path always as it is done here

  Any breaking change

  No

  Is this change easily revertible

  Yes

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 50.00000% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 68.85%. Comparing base (9f85057) to head (350a829). Report is 1 commits behind head on master.

Files	Patch %	Lines
main.go	0.00%	4 Missing :warning:
runner/config.go	75.00%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #590 +/- ## ========================================== + Coverage 67.12% 68.85% +1.72% ========================================== Files 12 12 Lines 1080 1095 +15 ========================================== + Hits 725 754 +29 + Misses 266 250 -16 - Partials 89 91 +2 ```

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[kareemmahlees]

I can't test the error case of WithArgs because filepath.Abs's implementation varies by platform.