Hello!

Nalaginrut reported that Guix fails to build with Guile 2.2, which was a
bit of a shame, hence commits e465d9e19087ab150f7e31f21c09e4a147b93b36
and 9d126aa2b504bb9fad536eac186805ff623e96be.

Now, the hack in build-aux/compile-all.scm doesn’t quite work with 2.2,
and it was already quite fragile.

So I think we need a different approach.  A more robust approach that
comes to mind would be to look at our module dependency graph (with help
from (guix modules)), run N Guile processes (instead of threads), and
have each of them build a subset of the graph.  It would essentially
require us to reimplement a subset of Make (or guix-daemon).

I’ve tried generating makefile rules from module dependencies.  That’s
pretty cool, but compilation of the package modules remains damn slow
(2nd patch attached).

What do people think?  Anyone has a better idea?

The attached patch allows us to build the modules sequentially but in
topologically-sorted order, which means we can avoid the ugly
load-modules-first workaround.  Still, it’s a bit too slow.

Ludo’.