DMD as cross-compiler

[Iain Buclaw]

On Wednesday, 11 November 2020 at 10:49:54 UTC, Walter Bright 
wrote:
> I realized that DMD is pretty close to being a cross-compiler, 
> and won't need much work to go the rest of the way. I 
> anticipate it could be very convenient when inconvenient to get 
> the native DMD installed. It also should be useful for 
> debugging problems with test suite failures :-/
>
> Much of the static versioning in the backend is the result of 
> converting it from C with its #if statements. Being done with 
> all that preprocessor legacy will be nice.
>
> Working on a series of incremental PRs to make this happen.

Jonathon raised today that FreeBSD 11 -> FreeBSD 12 as been an 
issue for cross-compiling since the build scripts were replaced 
by a build.d source file.

It seems that cross-compiling between incompatible versions of 
libc on the same platform still needs to be sorted out.