Co-simulation in pb-flow

[jianyicheng]

Added co-simulation for pb-flow

• Get baseline results from C code
• Check correctness for Phism
• Get timing results for Phism

[jianyicheng]

To run co-simulation for Polybench, need to run the following before start Vitis HLS:
export LIBRARY_PATH=/usr/lib/x86_64-linux-gnu:$LIBRARY_PATH
This has been added into the Dockerfile, but need to be added into the doc for general building process.

Details: https://forums.xilinx.com/t5/High-Level-Synthesis-HLS/Vivado-HLS-C-simulation-and-C-RTL-cosimulation-running-Debian/td-p/1019856