fix protobuf build script
fix protobuf build script

google/keytransparency,cesarghali/keytransparency,gdbelvin/keytransparency,alsophian/keytransparency,AMarcedone/keytransparency,google/keytransparency,gdbelvin/keytransparency,AMarcedone/keytransparency,cesarghali/keytransparency,alsophian/keytransparency