WSL: fix downloader plugin

[jkroepke]

What this PR does / why we need it: Fix downloader plugin, if helm is installed as native binary inside WSL

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #477

Special notes for your reviewer:

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 87.42%. Comparing base (d1b66f7) to head (839d3be).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
scripts/lib/common.sh	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #482      +/-   ##
==========================================
+ Coverage   87.33%   87.42%   +0.08%     
==========================================
  Files          22       22              
  Lines         845      843       -2     
==========================================
- Hits          738      737       -1     
+ Misses        107      106       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.