Reproducible builds of D compilers

[Pjotr Prins via Digitalmars-d]

At Dconf we had a discussion on creating reproducible builds of 
the D compilers. One thing that is required is bootstrapping the 
build. In GNU Guix we start from a working C compiler which is a 
reasonable starting point (it could have been LISP instead ;)

For D this means that even if all components of the compilers are 
written in D we should have a (chain of) compilation steps that 
can be initiated from a C or C++ compiler. This is still the case 
today, but I want to highlight this point here so we do not lose 
that facility.

GNU Guix can be used as a reproducible reference build system 
where we capture the bootstrapping process nicely and test the 
builds on the build farm(s) whenever something changes.