Include of gtest_prod.h only building unittests

Change-Id: I605ba14fa7e205158aef671c98938b911362b5b6
Reviewed-on: https://weave-review.googlesource.com/2329
Reviewed-by: Jacob Marble <jacobmarble@google.com>
Reviewed-by: Alex Vakulenko <avakulenko@google.com>
diff --git a/tests.mk b/tests.mk
index 1ae3b81..563b94b 100644
--- a/tests.mk
+++ b/tests.mk
@@ -26,7 +26,7 @@
 
 $(weave_unittest_obj_files) : out/$(BUILD_MODE)/%.o : %.cc third_party/include/gtest/gtest.h
 	mkdir -p $(dir $@)
-	$(CXX) $(DEFS_$(BUILD_MODE)) $(INCLUDES) $(CFLAGS) $(CFLAGS_$(BUILD_MODE)) $(CFLAGS_CC) -c -o $@ $<
+	$(CXX) $(DEFS_TEST) $(INCLUDES) $(CFLAGS) $(CFLAGS_$(BUILD_MODE)) $(CFLAGS_CC) -c -o $@ $<
 
 out/$(BUILD_MODE)/libweave_testrunner : $(weave_unittest_obj_files) $(third_party_chromium_crypto_unittest_obj_files) $(third_party_chromium_base_unittest_obj_files) out/$(BUILD_MODE)/libweave_common.a out/$(BUILD_MODE)/libweave-test.a
 	$(CXX) -o $@ $^ $(CFLAGS) -lcrypto -lexpat -lgmock -lgtest -lpthread -lrt -Lthird_party/lib
@@ -41,7 +41,7 @@
 
 $(weave_exports_unittest_obj_files) : out/$(BUILD_MODE)/%.o : %.cc third_party/include/gtest/gtest.h
 	mkdir -p $(dir $@)
-	$(CXX) $(DEFS_$(BUILD_MODE)) $(INCLUDES) $(CFLAGS) $(CFLAGS_$(BUILD_MODE)) $(CFLAGS_CC) -c -o $@ $<
+	$(CXX) $(DEFS_TEST) $(INCLUDES) $(CFLAGS) $(CFLAGS_$(BUILD_MODE)) $(CFLAGS_CC) -c -o $@ $<
 
 out/$(BUILD_MODE)/libweave_exports_testrunner : $(weave_exports_unittest_obj_files) out/$(BUILD_MODE)/libweave.so out/$(BUILD_MODE)/libweave-test.a out/$(BUILD_MODE)/src/test/weave_testrunner.o
 	$(CXX) -o $@ $^ $(CFLAGS) -lcrypto -lexpat -lgmock -lgtest -lpthread -lrt -Lthird_party/lib -Wl,-rpath=out/$(BUILD_MODE)/