Support building for OpenBSD host

[reezer]

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• The PR has no duplicates (please search among the Pull Requests
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• The PR follows
  our contributing guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• UPGRADING.md has been updated with a migration guide (for breaking changes)
• configuration.schema.json updated if new parameters are added.

What kind of change does this PR introduce?

GOOS=openbsd go build ./.... will not fail anymore and build a binary

What is the current behavior?

GOOS=openbsd go build ./.... fails with:

# github.com/arduino/arduino-cli/internal/locales
internal/locales/detect.go:24:9: undefined: getLocaleIdentifier

What is the new behavior?

An arduino-cli binary is created.

Does this PR introduce a breaking change, and is titled accordingly?

No

Other information

It might make sense to do the same change for NetBSD and DragonFly as well. However this doesn't seem to currently fix compilation. Maybe it makes sense to create an _other.go or _unsupported.go or _bsd.go file so people right away see the actual error instead of the file/os target not existing?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.45%. Comparing base (fb6bae1) to head (a45b925).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3208      +/-   ##
==========================================
+ Coverage   69.43%   69.45%   +0.01%     
==========================================
  Files         252      252              
  Lines       19565    19584      +19     
==========================================
+ Hits        13585    13602      +17     
+ Misses       4719     4712       -7     
- Partials     1261     1270       +9     

Flag	Coverage Δ
unit	69.45% <ø> (+0.01%)	⬆️

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