cocos 编译LOCAL_SRC_FILES points to a missing file

The following directory exists:

$NDK\sources\cxx-stl\gnu-libstdc++\4.8

while the following doesn't:

$NDK\sources\cxx-stl\gnu-libstdc++\4.9

leading to the following error when I try to compile with APP_STL=gnustl_static and NDK_TOOLCHAIN_VERSION = 4.9 in Application.mk:

Android NDK: ERROR:C:/AndroidNDK/sources/cxx-stl/gnu-libstdc++/Android.mk:gnustl_static: LOCAL_SRC_FILES points to a missing file
Android NDK: Check that C:/AndroidNDK/sources/cxx-stl/gnu-libstdc++/4.9/libs/armeabi-v7a/thumb/libgnustl_static.a exists  or that its path is correct

==================================================================================

当使用这条命令cocos compile -p android --ap android-21编译cocos android时会出现上述问题
需要制定toolchain版本，然后就可以顺利编译了~
cocos compile --android-studio --target android-21 --ap android-21 --ndk-mode debug
--ndk-toolchain arm-linux-androideabi-4.8 --platform android --app-abi armeabi --src D:\DevProject\cocos2dx_workspacecos2dx_workspace\mygame

具体原因是对应目录下没有4.9版本目录找不到路径。