Hi Nico,
My WaRP7 builds are failing because meta-clang has dropped warrior support from its master branch. The same problem will happen in oe-rpb's warrior branch, as you're also using meta-clang master.
The meta-clang warrior branch is quite old and is missing a lot of the patches from master that I've been building with for a long time. I wanted to send a patch to fix oe-rpb, but I don't know if you'd prefer to use the last known good SHA from the meta-clang master branch, or to use their warrior branch.
I'm not using clang, so for my WaRP7 builds, I've just reverted to the warrior branch to see if it builds, at least.
Cheers,
Ryan.