Add C++ compiler warning options

Change-Id: I0d79d450c5cca887d02a1087128c1d3eb0bf0b7f
diff --git a/native/jni/Android.mk b/native/jni/Android.mk
index 7827db3..3b3da96 100644
--- a/native/jni/Android.mk
+++ b/native/jni/Android.mk
@@ -28,7 +28,8 @@
 LOCAL_C_INCLUDES += $(LOCAL_PATH)/$(LATIN_IME_SRC_DIR)
 
 LOCAL_CFLAGS += -Werror -Wall -Wextra -Weffc++ -Wformat=2 -Wcast-qual -Wcast-align \
-    -Wwrite-strings -Wfloat-equal -Wpointer-arith -Winit-self -Wredundant-decls -Wno-system-headers
+    -Wwrite-strings -Wfloat-equal -Wpointer-arith -Winit-self -Wredundant-decls \
+    -Woverloaded-virtual -Wstrict-null-sentinel -Wsign-promo -Wno-system-headers
 
 ifeq ($(TARGET_ARCH), arm)
 ifeq ($(TARGET_GCC_VERSION), 4.6)