[PATCH] eng: Add build system chapter

[Chris Johns]

On 11/11/19 8:45 pm, Sebastian Huber wrote:
> On 08/11/2019 23:48, Chris Johns wrote:[...]
>> 3. Is the ${} expansion something you have implemented? It is a nice feature.
> [...]
> 
> With standard Python the substitution itself is a one liner:
> 
>     def substitute(self, ctx, value):
>         if isinstance(value, str):
>             try:
>                 return Template(value).substitute(ctx.env)
>             except Exception as e:
>                 ctx.fatal(
>                     "In item '{}' substitution in '{}' failed: {}".format(
>                         self.uid, value, e
>                     )
>                 )
>         return value
> 

Does this support nested defines?

The RSB and rtemstoolkit macros recursively expand as it was a something I found
needed and useful ...

https://git.rtems.org/rtems-tools/tree/rtemstoolkit/macros.py#n471

Chris