Add ImportC compiler to dmd

[Adam D. Ruppe]

On Sunday, 9 May 2021 at 20:57:06 UTC, Walter Bright wrote:
> If you could add a C compiler to dmd with 3000 lines of code,

As of the time of this writing it has already grown to:

https://github.com/dlang/dmd/pull/12507

+3,905 −42

30% overbudget just three days after the announcement. I stand by 
my prediction that this is going to end up a LOT bigger than it 
looked at first.