[VTA] Workaround for Autotuning with One PYNQ Z1 Board

Development
16

Hi @thkim

I use su to start the tracker and modify the corresponding environment variables.

TVM_HOME="/home/xilinx/tvm"
VTA_HW_PATH="/home/xilinx/tvm/3rdparty/vta-hw"
PYTHONPATH="/home/xilinx/tvm/python:/home/xilinx/tvm/topi/python:/home/xilinx/tvm/vta/python"