WEIGHTS_DIR redefinition

Created by: KOVI89alipes

WEIGHTS_DIR is hard-coded in https://github.com/fastmachinelearning/hls4ml/blob/f31b52fca2a85deb8d1b91d637636a365151194f/hls4ml/templates/vivado/nnet_utils/nnet_helpers.h#L35 And it requires copying or symlinking weights folder into the build folder whenever the model function is compiled from the outside of HLS4ML project.

Possible fix:

#ifndef WEIGHTS_DIR
#define WEIGHTS_DIR "weights"
#endif

In this case WEIGHTS_DIR can be redefined during compilation

Another option - do not store TXT files, but dump weights into includes