Per-architecture CAS servers
Buildstream should support having different CAS servers for different architectures. Discussed earlier with @jjardon that not all builder types are equal in eg freedesktop-sdk build system. You can apparently fairly easily have starvation with ARM builders. This results in some artifacts in CAS being more computationally expensive than others and should have higher likelihood of being preserved. As CAS itself should most likely not have the prioritization logic, an idea was raised of having multiple CAS servers/daemons behind hard disks so you would have separate buckets with separate quotas.