Don't use GTEST_OS_LINUX on Darwin

Change-Id: If77118591daa7b474e6989e03109ea32ddd357b2
diff --git a/core/host_test_internal.mk b/core/host_test_internal.mk
index e4fa4c5..6c52e64 100644
--- a/core/host_test_internal.mk
+++ b/core/host_test_internal.mk
@@ -5,7 +5,7 @@
 LOCAL_CFLAGS_windows += -DGTEST_OS_WINDOWS
 LOCAL_CFLAGS_linux += -DGTEST_OS_LINUX
 LOCAL_LDLIBS_linux += -lpthread
-LOCAL_CFLAGS_darwin += -DGTEST_OS_LINUX
+LOCAL_CFLAGS_darwin += -DGTEST_OS_MAC
 LOCAL_LDLIBS_darwin += -lpthread
 
 LOCAL_CFLAGS += -DGTEST_HAS_STD_STRING -O0 -g