Building the compiler in 2 seconds with `dmd -i`

[Dany12L]

On Friday, 19 May 2023 at 20:30:12 UTC, Dennis wrote:
> On Friday, 19 May 2023 at 09:51:39 UTC, Dennis wrote:
>> Eventually I hope to make just `dmd -i dmd/mars.d` work, I'll 
>> see how close I can get to that.
>
> It's now down to this!
> ```
> dmd -i dmd/mars.d -of=../../dmd dmd/eh.d -Jdmd/res -J../..
> ```

I think we should try to remove the import files which are 
definitely baggage, VERSION and SYSCONFDIR.imp could be converted 
to a auto-generated .D with a enum inside