fix: use xdg-open for opening URL on FreeBSD

[mord0d]

Checklist

Required

• I wrote the PR title in conventional commit format.
• I ran the code formatter.
• I linked any relevant issues using github keyword syntax so it can be closed automatically.
• I have committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.

Optional

Purpose of change

Fixes #5585

Allows to build source code on FreeBSD (tested on 14.1-RELEASE-p5).

Describe the solution

Describe alternatives you've considered

Testing

Additional context

[RoyalFox2140]

I am 100% unqualified to understand any of this despite touching the build matrix a bit. I'll send this to people who can take a good look at it so we make sure it gets reviewed.