Setting model size

[mtfurlan]

Right now if you want to specify model size, you have to do a janky workaround.

Is it okay if I make a PR to check for a model_size key set by board_build.model_size in platformio.ini?

Options would be small, medium, large, huge, from the sdcc manual, page 38, section 3.3.6 MCS51 Options

I find it confusing to specify default values to a compiler, so I would rather omit --model-whatever unless the user chooses something.
It looks like the only way to do that would be to add default as a value in each board json file.

How do I inform users what the available options for model are?
The current documentation page just says

You can override default CH559 settings per build environment using board_*** option, where *** is a JSON object path from board manifest CH559.json. For example, board_build.mcu, board_build.f_cpu, etc.

But all the current options are numbers with units so it's pretty clear.
Do I just have to make another PR against that doc page with a description of what model does, and what the available options are?