Patch for rtems_waf to support build configurations in libbsd

[Chris Johns]

On 05/04/2018 23:29, Christian Mauderer wrote:
> 
> I now managed to build multiple configurations for libbsd. But I needed
> the per-bsp-classes from the rtems_waf/rtems.py init function so that I
> can derive further classes of them. So I added a hook to the init
> function that is executed at the end.
> 
> If you want to know where I needed that hook, you can take a look at the
> latest version of my ticket branch. Note that I still have to merge a
> lot of commits on this branch to only a few clean ones. Basically every
> commit that starts with FIXME:
> https://git.rtems.org/christianm/rtems-libbsd.git/tree/wscript?h=ticket-3351&id=5aca4e1c04cc596a1202ff880ec186ce205fd817#n154

Looks good.

> I added some basic notes regarding how the variants work (or at least
> how I understood it) in the other thread:
> https://lists.rtems.org/pipermail/devel/2018-April/020843.html
> 
> Would you see a better / simpler solution to that problem? If not: Would
> you accept that patch?

The patch is a good and simple improvement and yes I will accept it with the
minor changes I have requested against the patch.

Thank you for the changes and the analysis.

Chris