4.0 regression: Protoc check breaks contribs build system
Protoc check is always performed even if we don't depend on it
../../contrib/src/protobuf/rules.mak:19: *** /usr/bin/protoc version 3.5.0 doesn't match the protobuf 3.1.0 we're building.
The way it is performed, check code has a chicken and egg problem