...

CMakeLists.txt

@@ -32,6 +32,11 @@ else()
     if(APPLE)
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-shorten-64-to-32")
     endif()
+
+    # if android, use -Os
+    if(ANDROID)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Os")
+    endif()
 endif()
 
 include_directories(${CMAKE_CURRENT_LIST_DIR}/include)