Update compiler/linker options to use pkg-config in C++ examples

examples/cpp/helloworld/Makefile

@@ -17,16 +17,16 @@
 HOST_SYSTEM = $(shell uname | cut -f 1 -d_)
 SYSTEM ?= $(HOST_SYSTEM)
 CXX = g++
-CPPFLAGS += -I/usr/local/include -pthread
+CPPFLAGS += `pkg-config --cflags protobuf grpc`
 CXXFLAGS += -std=c++11
 ifeq ($(SYSTEM),Darwin)
-LDFLAGS += -L/usr/local/lib `pkg-config --libs grpc++ grpc`       \
-           -lgrpc++_reflection \
-           -lprotobuf -lpthread -ldl
+LDFLAGS += -L/usr/local/lib `pkg-config --libs protobuf grpc++ grpc`\
+           -lgrpc++_reflection\
+           -ldl
 else
-LDFLAGS += -L/usr/local/lib `pkg-config --libs grpc++ grpc`       \
-           -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed \
-           -lprotobuf -lpthread -ldl
+LDFLAGS += -L/usr/local/lib `pkg-config --libs protobuf grpc++ grpc`\
+           -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed\
+           -ldl
 endif
 PROTOC = protoc
 GRPC_CPP_PLUGIN = grpc_cpp_plugin

examples/cpp/route_guide/Makefile

@@ -17,16 +17,16 @@
 HOST_SYSTEM = $(shell uname | cut -f 1 -d_)
 SYSTEM ?= $(HOST_SYSTEM)
 CXX = g++
-CPPFLAGS += -I/usr/local/include -pthread
+CPPFLAGS += `pkg-config --cflags protobuf grpc`
 CXXFLAGS += -std=c++11
 ifeq ($(SYSTEM),Darwin)
-LDFLAGS += -L/usr/local/lib `pkg-config --libs grpc++`            \
-           -lgrpc++_reflection \
-           -lprotobuf -lpthread -ldl
+LDFLAGS += -L/usr/local/lib `pkg-config --libs protobuf grpc++`\
+           -lgrpc++_reflection\
+           -ldl
 else
-LDFLAGS += -L/usr/local/lib `pkg-config --libs grpc++`            \
-           -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed \
-           -lprotobuf -lpthread -ldl
+LDFLAGS += -L/usr/local/lib `pkg-config --libs protobuf grpc++`\
+           -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed\
+           -ldl
 endif
 PROTOC = protoc
 GRPC_CPP_PLUGIN = grpc_cpp_plugin