Porting work for DragonFly BSD

[tuxillo]

This adds DragonFly BSD to the list of BSDs so that lima-vm can be built (lima-vm/lima#892)

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (0f9eb93) 72.77% compared to head (480d037) 72.77%.

❗ Current head 480d037 differs from pull request most recent head 754e1cd. Consider uploading reports for the commit 754e1cd to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #510   +/-   ##
=======================================
  Coverage   72.77%   72.77%           
=======================================
  Files          91       91           
  Lines        5777     5777           
=======================================
  Hits         4204     4204           
  Misses       1398     1398           
  Partials      175      175           

Files Changed	Coverage Δ
dhcpv4/nclient4/conn_unix.go	63.51% <ø> (ø)

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[pmazzini]

Can you sign the commit? Example:

• Ensure you have a local copy of your branch by checking out the pull request locally via command line.
• In your local branch, run: git rebase HEAD~1 --signoff
• Force push your changes to overwrite the branch: git push --force-with-lease origin feat-dragonflybsd-support

Ref: https://github.com/insomniacslk/dhcp/pull/510/checks?check_run_id=15920848080