Porting work for DragonFly BSD

[tuxillo]

This adds DragonFly BSD to the list of BSDs so that lima-vm can be built (https://github.com/lima-vm/lima/issues/892)

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

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

:exclamation: 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

```diff @@ 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](https://app.codecov.io/gh/insomniacslk/dhcp/pull/510?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=insomniac) | Coverage Δ | | |---|---|---| | [dhcpv4/nclient4/conn\_unix.go](https://app.codecov.io/gh/insomniacslk/dhcp/pull/510?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=insomniac#diff-ZGhjcHY0L25jbGllbnQ0L2Nvbm5fdW5peC5nbw==) | `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