cmake: don't fetch Protobuf submodules
cmake: don't fetch Protobuf submodules

or-tools/or-tools,or-tools/or-tools,google/or-tools,or-tools/or-tools,or-tools/or-tools,or-tools/or-tools,google/or-tools,or-tools/or-tools,google/or-tools,google/or-tools,google/or-tools,google/or-tools