extend pragma(msg) with writing to file

[Araq]

On Friday, 7 October 2022 at 21:45:25 UTC, TheGag96 wrote:
> On Thursday, 6 October 2022 at 12:08:16 UTC, bauss wrote:
>> [...]
>
> But we've already basically been there for decades through:
>
> * `configure` scripts from autotools
> * Makefiles
> * Ad-hoc shell/Python build scripts
> * `dub.json`/`dub.sdl` calling out to shell
>
> [...]

Fwiw Nim supports that since about a decade now... It's of course 
harder to be excited about something that already actually exists 
and works. ;-)