Turns out it works fine out of the box if you have pkgconf installed.

root@freebsd-10:/ # pkg install -y pkgconf
Updating FreeBSD repository catalogue...
FreeBSD repository is up-to-date.
All repositories are up-to-date.
Checking integrity... done (0 conflicting)
The following 1 package(s) will be affected (of 0 checked):

New packages to be INSTALLED:
        pkgconf: 0.9.12

The process will require 56 KiB more space.
[1/1] Installing pkgconf-0.9.12...
[1/1] Extracting pkgconf-0.9.12: 100%
root@freebsd-10:/ # gem install ruby-libvirt
Fetching: ruby-libvirt-0.5.2.gem (100%)
Building native extensions.  This could take a while...
Successfully installed ruby-libvirt-0.5.2
Parsing documentation for ruby-libvirt-0.5.2
Installing ri documentation for ruby-libvirt-0.5.2
Done installing documentation for ruby-libvirt after 0 seconds
1 gem installed
 

On Tue, Oct 20, 2015 at 12:49 PM, Roman Bogorodskiy <bogorodskiy@gmail.com> wrote:
  Rickard von Essen wrote:

> Hi,
>
> Installing the ruby-libvirt gem fails on FreeBSD 10.2 since it can't locate
> the lib and include dir. Installing with:
>   gem install ruby-libvirt --
> --with-libvirt-include=/usr/local/include/libvirt
> --with-libvirt-lib=/usr/local/lib/libvirt.so
> works fine.
>
> It would be great if this worked out of the box, e.g. detects that it is
> building on BSD and applies the above settings as default, or at least it
> could be provided as a hint if running make fails to guide ruby noobs, like
> me.

Hi Rickard,

I tried it on my system and it seems to work fine without manually
providing include and lib paths.

>From what I can see, it uses pkg-config to detect CFLAGS and LDFLAGS (I
could be wrong here though because I'm not familiar with Ruby).

Could you please check if you have this working:

$ pkg-config --libs --cflags libvirt
-I/usr/local/include -L/usr/local/lib -lvirt
$

If that does not work, could you please describe how did you do the
libvirt installation on your system?

Thanks,

Roman Bogorodskiy