message: fix(makefile): fix main makefile
diff: # WARN: maybe difficult to install ccache in some systems
  #CXX = ccache g++
  -CXX = /usr/local/bin/g++
  -CC = /usr/local/bin/gcc
  +CXX = g++
  +CC = gcc
  #the optimazition level of gcc/g++
  #http://blog.csdn.net/hit_090420216/article/details/44900215
  #NOTICE: -O2 is recommended, while -O3(add loop-unroll and inline-function) is dangerous
  #when developing, not use -O because it will disturb the normal
  #routine. use it for test and release.
  -# CFLAGS = -c -Wall -O2 -pthread -std=c++11
  -# EXEFLAG = -O2 -pthread -std=c++11
  -CFLAGS = -c -Wall -O0 -g -pthread -std=c++11
  -EXEFLAG = -O0 -g -pthread -std=c++11
  +CFLAGS = -c -Wall -O2 -pthread -std=c++11
  +EXEFLAG = -O2 -pthread -std=c++11
  #-coverage for debugging
  # CFLAGS = -c -Wall -pthread -g3 -std=c++11 -gdwarf-2
  # EXEFLAG = -pthread -g3 -std=c++11 -gdwarf-2
  @@ -700,8 +698,8 @@ $(objdir)Server.o: Server/Server.cpp Server/Server.h $(objdir)Socket.o $(objdir)
  $(objdir)APIUtil.o: GRPC/APIUtil.cpp GRPC/APIUtil.h Database/Database.h Database/Txn_manager.h Util/Util.h $(lib_antlr)
  $(CXX) $(CFLAGS) GRPC/APIUtil.cpp $(inc) -o $(objdir)APIUtil.o -DUSE_BOOST_REGEX $(def64IO) $(openmp)
  -$(objdir)grpc.pb.o: GRPC/grpc.pb.CXX GRPC/grpc.pb.h $(lib_antlr) $(lib_workflow)
  - $(CXX) $(CFLAGS) GRPC/grpc.pb.CXX $(inc) -o $(objdir)grpc.pb.o -DUSE_BOOST_REGEX $(def64IO) $(openmp)
  +$(objdir)grpc.pb.o: GRPC/grpc.pb.cc GRPC/grpc.pb.h $(lib_antlr) $(lib_workflow)
  + $(CXX) $(CFLAGS) GRPC/grpc.pb.cc $(inc) -o $(objdir)grpc.pb.o -DUSE_BOOST_REGEX $(def64IO) $(openmp)
  $(objdir)grpcImpl.o: GRPC/grpcImpl.cpp GRPC/grpcImpl.h GRPC/grpc.srpc.h GRPC/APIUtil.h Database/Database.h Database/Txn_manager.h Util/Util.h $(lib_antlr) $(lib_workflow)
  $(CXX) $(CFLAGS) GRPC/grpcImpl.cpp $(inc) -o $(objdir)grpcImpl.o -DUSE_BOOST_REGEX $(def64IO) $(openmp)
  