[Builder] Optional YAML based build configuration flow

[bwintermann]

Draft for a YAML based build file, replacing the need for Python scripts, but not replacing it (keeping backwards compatibility, so writing a build.py script is still possible in case your build flow is more complicated). Would work on this occasionally unless @iksnagreb already has something similar.

I think it would be cleaner and presents a nice interface with software written around it which does not necessarily use Python.

Tasks that would need to be done:

• YAML to BuildDataflowCfg conversion function
• Integration into run-docker.sh so that the correct FINN function is called (ideally you can pass both build.py and build.yaml to ./run-docker.sh build_custom and the script automatically can differentiate)
• Implement every option that BuildDataflowCfg has to be settable by the YAML file
• Replace print statements by logger statements when First set of small QOL improvements #14 is merged
• Tests for the conversion function

An example build.yaml could look like this:

config:
  general:
    synth_clk_period_ns: 5.5
    board: U280
    platform: Alveo
    vitis_opt_strategy: PERFORMANCE
    specialize_layers_config_file: specialization.json
    folding_config_file: folding.json
    generate_outputs:
        - BITFILE
        - DEPLOYMENT_PACKAGE
        - ...
  
  build_steps:
    - step_convert_qonnx
    - step_streamline
    - step_create_dataflow_partition
    - step_specialize_layers
    - step_generate_estimate_reports
    - step_hw_codegen
    - step_hw_ipgen
    - custom_steps.step_my_great_function
    - ...

[iksnagreb]

unless @iksnagreb already has something similar.

I actually kind of already have, except for the build_steps as these sometimes require stuff computed/inserted/configured from other sources which is not easy to do with static YAML configuration (some of my custom build steps are actually build step generators...). However, the way I currently handle the YAML-based config is to simply **config into the DataflowBuildConfig, so there is probably something to refine... I will have a look at your draft, maybe we could/should discuss this further. I am also not sure what @fpjentzsch might already have in place in terms of JSON-based infrastructure...

[bwintermann]

Sounds great, lets maybe discuss this futher next week, maybe we can make it flexible enough to even allow build steps generator in the YAML itself. I think in terms of JSON this should be easy to integrate since we can quite easily convert the two formats into each other.