Use a precompiled `protoc` toolchain

we have just updated the Envoy repo to make use of precompiled `protoc` which speeds a load of things up

recompiling the go protos i immediately noticed that i was compiling protoc

one option is using protobuf from `rules_proto` which makes use of the precompiled bins but this then ties you to their version of protobuf

another option is to patch protobuf, this is what Envoy does