bug#39503: Supporting elf-debuginfod (debug symbol server)

[Ludovic Courtès]

Hello Guix!

I’ve just watched Mark’s very nice talk about debuginfod and and I’d
like to work towards running an instance of it on ci.guix.gnu.org:

  https://fosdem.org/2020/schedule/event/debugging_debuginfod/

What’s missing today is configuring GCC with ‘--enable-linker-build-id’
(which is not the default, unlike what Mark says in the talk :-)).

If we do that, I wonder if we can stop using ‘.gnu_debuglink’ (see the
‘strip’ phase in (guix build gnu-build-system)).

Also, I suspect build IDs wouldn’t mesh well with grafting: unless we
rewrite them, the same build ID would match both the ungrafted and the
grafted variant.  Is that a problem?  Not sure.  (Currently (guix build
debug-link) recomputes ‘.gnu_debuglink’ upon grafting so that the links
remain valid.)

Thoughts?

Thanks,
Ludo’.

PS: I found Eelco Dolstra’s dwarffs to be very smart, too!
    https://github.com/edolstra/dwarffs