Fixing protobuf definitions on Linux. New protobuf requires C++17

[gapisback]

@jlmucb reports this issue based on some of his work to get CFCC / protobuf working on a Linux implementation. (Raspberry PI? Get clarification.)

I just spent an incredibly frustrating day fixing protobuf on my Linux machine. The new protobuf requires C++17.

After I rebuilt gflags, googletest, abseil and protobuf under C++17, everything compiled but I got a load of undefined symbols. I was within 30 seconds of hitting my computer when I discovered a fix I don't quite understand. The earlier command is marked * and the working command (for the new protobuf only) is marked ** below. So, when you start using the new protobuf talk to me otherwise you might be moved to violence.

I discovered this in another project but I'll probably have to fix this in the certifier.

[ NOTE: P.S. It's not exactly clear what the code snippet below is trying to say. Figure out details from John and update issue. ]

ifndef NEWPROTOBUF
CFLAGS=$(INCLUDE) -O3 -g -Wall -std=c++11 -Wno-unused-variable -D X64
CFLAGS1=$(INCLUDE) -O1 -g -Wall -std=c++11 -Wno-unused-variable -D X64
else
CFLAGS=$(INCLUDE) -O3 -g -Wall -std=c++17 -Wno-unused-variable -D X64
CFLAGS1=$(INCLUDE) -O1 -g -Wall -std=c++17 -Wno-unused-variable -D X64
endif
CC=g++
LINK=g++
PROTO=protoc
AR=ar

# build the library later
tobj=   $(O)/acl.o $(O)/acl.pb.o $(O)/test_acl.o

ifdef NEWPROTOBUF
export LD_LIBRARY_PATH=/usr/local/lib
LDFLAGS= -L/usr/local/lib `pkg-config --cflags --libs protobuf` -lgtest -lgflags -lpthread
else
export LD_LIBRARY_PATH=/usr/local/lib
LDFLAGS= -L/usr/local/lib -lprotobuf -lgtest -lgflags -lpthread
endif