Bump the minimal version required to compile DMD to 2.076.1

[Thomas Mader]

On Friday, 12 January 2018 at 16:13:39 UTC, Seb wrote:
> Motivation
> ----------
>
> 1) It's required for Walter's work on using -betterC for the 
> backend conversion:
>
> https://github.com/dlang/dmd/pull/6907
>
> 2) We start to run into random failures lately, e.g.
>
> https://github.com/braddr/d-tester/issues/63
> https://github.com/dlang/dmd/pull/7569#issuecomment-356992048
>
> 3) There's also WIP to move dmd-cxx to 2.076.1:
>
> https://github.com/dlang/dmd/pull/7595
>
> So if we have to bump the minimal dmd version required to build 
> DMD anyways for (1), let's be clear about it and state it.
>
> Anyone objecting?

TLDR; I hope dmd needs a properly maintained bootstrap compiler 
branch with release tags of new versions every now and then as 
ldc does.

For packaging dmd on NixOS it is important to have a bootstrap 
compiler because the entire package tree of the distribution is 
build from scratch and no custom binaries can be used. (Well you 
can patch binaries with patchelf but that's not very nice and 
should probably only used for binary blobs)

Currently dmd 2.067.1 is used on NixOS as a bootstrap compiler 
and the last time I tried dmd-cxx it didn't work because of some 
build problems.
dmd 2.067.1 doesn't build with gcc6 which is the default for 
NixOS. This is not much of a problem because it can be easily 
overwritten to use gcc5 for the bootstrap compiler but still.
I also needed to patch things for the newest dmd version which I 
am slowly trying to upstream but since there are no bootstrap 
backports I can't get rid of those patches in the bootstrap 
package.

Which frontend version such a bootstrap branch has doesn't matter 
for me as long as it is maintained and I can build the newest 
version of dmd and all unit tests run successfully.