BuildStream artifact-cache SSL issues
Currently the artifact-cache uses the default SSL install for the GRPC python library.
This is known to cause performance issues at scale: https://github.com/grpc/grpc/blob/master/doc/ssl-performance.md, freedesktop-sdk/infrastructure/infrastructure!31 (merged)
The solution is to build the cache with the system ssl:
environment:
GRPC_PYTHON_BUILD_SYSTEM_OPENSSL: "true"
GRPC_PYTHON_BUILD_WITH_CYTHON: "1"