ncnn 不支持 mxnet mobilefacenet 一些层？

[ronyuzhang]

error log：
BlockGrad not supported yet!
one_hot not supported yet!

depth=2

off_value=0.0

on_value=1.0

pick not supported yet!

axis=1

where not supported yet!

[nihui]

训练相关的op，转换时可以不用管，用的时候做成noop
https://github.com/Tencent/ncnn/wiki/FAQ-ncnn-throw-error#layer-xyz-not-exists-or-registered

[sf7509]

参照代码加上 Noop

但是android下ndk-build 出现：

cnn/jni/test.cpp:typeinfo for Noop: error: undefined reference to 'typeinfo for ncnn::Layer'