Fix Make build under Linux (Ubuntu) (tensorflow#4260)

* Fix Make build under Linux (Ubuntu)

* Add missing files to the list of source to build.

* Add the -fPIC flag under Linux (ignored when no necessary).

* Fix Make build under Linux (Ubuntu)

* Add missing files to the list of source to build.

* Add the -fPIC flag under Linux (ignored when no necessary).

* Refactor Makefile change to comply with guidance.

https://github.com/tensorflow/tensorflow/tree/master/tensorflow/contrib/makefile#fixing-makefile-issues

* Refactor Makefile change to comply with guidance.

https://github.com/tensorflow/tensorflow/tree/master/tensorflow/contrib/makefile#fixing-makefile-issues

Author: ic

tensorflow/contrib/makefile/Makefile

@@ -188,6 +188,7 @@ ifeq ($(HAS_GEN_HOST_PROTOC),true)
 	LIBFLAGS += -L$(MAKEFILE_DIR)/gen/protobuf-host/lib
 	export LD_LIBRARY_PATH=$(MAKEFILE_DIR)/gen/protobuf-host/lib
 endif
+	CXXFLAGS += -fPIC
 	LIBFLAGS += -Wl,--allow-multiple-definition -Wl,--whole-archive
 	LDFLAGS := -Wl,--no-whole-archive
 endif