fix multi_rule

still failing goma client build

  CXX(target) out/Debug/obj.target/lib/lib/goma_data_util.o
./lib/goma_data_util.cc:13:36: fatal error: prototmp/goma_data.pb.h: No such file or directory
 # include "prototmp/goma_data.pb.h"
                                    ^
compilation terminated.
2 files changed