fix(build): fix build on FreeBSD (#1639)

## Checklist

- [x] I have read the [contribution
guidelines](https://github.com/ooni/probe-cli/blob/master/CONTRIBUTING.md)
- [x] reference issue for this pull request:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=270020
- [ ] if you changed anything related to how experiments work and you
need to reflect these changes in the ooni/spec repository, please link
to the related ooni/spec pull request: <!-- add URL here -->
- [ ] if you changed code inside an experiment, make sure you bump its
version number

<!-- Reminder: Location of the issue tracker:
https://github.com/ooni/probe -->

## Description

The build of ooni-probe currently fails on FreeBSD because the compiler
cannot find some required symbols (C.SOCK_STREAM, C.AF_INET, C.AF_INET6
and C.AF_UNSPEC). This causes the package
[net/ooni-probe-cli](https://www.freshports.org/net/ooni-probe-cli/) to
be unavailable.

Fix this by including sys/socket.h when building on FreeBSD.

See also these FreeBSD bug reports (the second report also applies to Go
1.21 and Go 1.22):

- [270020: net/ooni-probe-cli: update 3.21.1 → 3.22.0, fix
build](https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=270020)
- [272643: lang/go120: Build of one port fails with could not determine
kind of name for C.AF_INET,
etc](https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=272643)

I took a bit of a shortcut for the fix in the first URL by omitting the
#ifdef as that patch would only exist in the FreeBSD port anyway. Both
URLs also discuss if this is a problem in OONI or Go itself.

---------

Co-authored-by: René Ladan <rene0+ooni@freedom.nl>

internal/netxlite/getaddrinfo_cgo.go

@@ -9,6 +9,7 @@ package netxlite
 
 #ifndef _WIN32
 #include <netdb.h> // for getaddrinfo
+#include <sys/socket.h> // for C.SOCK_STREAM and C.AF_*
 #else
 #include <ws2tcpip.h> // for getaddrinfo
 #endif