Identify system and remove --no-as-need if it is Mac OS

examples/cpp/helloworld/Makefile

@@ -29,12 +29,20 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 
+HOST_SYSTEM = $(shell uname | cut -f 1 -d_)
+SYSTEM ?= $(HOST_SYSTEM)
 CXX = g++
 CPPFLAGS += -I/usr/local/include -pthread
 CXXFLAGS += -std=c++11
+ifeq ($(SYSTEM),Darwin)
 LDFLAGS += -L/usr/local/lib `pkg-config --libs grpc++ grpc`       \
            -lgrpc++_reflection \
            -lprotobuf -lpthread -ldl
+else
+LDFLAGS += -L/usr/local/lib `pkg-config --libs grpc++ grpc`       \
+           -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed \
+           -lprotobuf -lpthread -ldl
+endif
 PROTOC = protoc
 GRPC_CPP_PLUGIN = grpc_cpp_plugin
 GRPC_CPP_PLUGIN_PATH ?= `which $(GRPC_CPP_PLUGIN)`

examples/cpp/route_guide/Makefile

@@ -29,12 +29,20 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 
+HOST_SYSTEM = $(shell uname | cut -f 1 -d_)
+SYSTEM ?= $(HOST_SYSTEM)
 CXX = g++
 CPPFLAGS += -I/usr/local/include -pthread
 CXXFLAGS += -std=c++11
+ifeq ($(SYSTEM),Darwin)
 LDFLAGS += -L/usr/local/lib `pkg-config --libs grpc++`            \
            -lgrpc++_reflection \
            -lprotobuf -lpthread -ldl
+else
+LDFLAGS += -L/usr/local/lib `pkg-config --libs grpc++`            \
+           -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed \
+           -lprotobuf -lpthread -ldl
+endif
 PROTOC = protoc
 GRPC_CPP_PLUGIN = grpc_cpp_plugin
 GRPC_CPP_PLUGIN_PATH ?= `which $(GRPC_CPP_PLUGIN)`