Current gwibber versions need >=vala-0.15.0 which isn't in portage yet.
Older version wouldn't build on nonpatched system libraries, will see if I can find a version in there that I can get to work somehow
I had a look at the current state of gwibber.
We'll probably not be able to include any recent build of gwibber in the repos. Not only do we need very recent vala, we'd also have to package a bunch of funky Ubuntu-libraries (libdee for example) just for gwibber with all recent versions of them not building properly with unpatched libraries.
If things change in Gwibber land or we get vala 0.15 and libdee into the tree for other reasons we might be able to get things running, right now I see the in tree gwibber as the only viable version for the forseable future.