Hence, I'm fine with you removing llvm-toolchain-9 and intentionally making beignet unbuildable, but please do *not* remove beignet from unstable for the time being. (It can be removed from testing.)
I'm not aware of a fix for this, and beignet is abandoned upstream and
mostly useful for old hardware (on newer hardware it is replaced by
intel-opencl-icd). However, I may look at it more later (and at least
try llvm-toolchain-12, though I'd expect that to be worse if anything).
