wip-arm-bootstrap: Reduced binary seed bootstrap

[Jan Nieuwenhuizen <janneke@gnu.org>]

Hi!

I pushed an initial wip-arm-bootstrap that builds up to tcc-boot:

--8<---------------cut here---------------start------------->8---
./pre-inst-env guix build -e '(@@ (gnu packages commencement) tcc-boot)'
--8<---------------cut here---------------end--------------->8---

Danny did a terrific job on armhf-linux support for GNU Mes and we are
getting close to release v0.23.  What's known to be missing is "setjmp"
support for tcc/gcc.  And, of course, for the Reduced binary seed
bootstrap to work on ARM!

In the previous status report

    https://lists.gnu.org/archive/html/bug-mes/2020-12/msg00002.html

I was stuck trying to get floats to work in tinycc but last weekend I
finally managed to bootstrap tcc, with long longs and floats enabled.
(this all took quite some effort).  Moving this into Guix should have
been almost trivial...but some silly "things" happened such as me
working off a dirty mes build tree; took me several days to find.

Anyway, the problem I'm looking at now is that while tcc-boot builds on
an ARM box, it does not build on aarch64-linux, i.e. this

--8<---------------cut here---------------start------------->8---
./pre-inst-env guix build --system=armhf-linux \
  -e '(@@ (gnu packages commencement) tcc-boot0)'
--8<---------------cut here---------------end--------------->8---

fails on overdrive1.

What's next?

  * Fix the aarch64-linux problem,
  * the current wip-arm-bootstrap is based on master: it needs to be
    rebased on core-updates,
  * the rest of the bootstrap needs attention,
  * which probably means supporting "setjmp" in the Mes C Library on ARM
  * remove binary seeds for binutils, gcc, glibc, coreutils&co,
  * verify the x86 bootstrap still works,
  * and the current version of tcc-boot0 applies two inexplicable hacks
      477134b1 HACK bootstrappable: ARM: "tccgen_ok".
      33b60f03 HACK bootstrappable: ARM: "tccpp_ok".
    that would be great to understand and get rid of,
  * and IWBN to fix Gash's stacktraces on failing exec
  configure: error: 'mescc' failed to compile conftest.c.
Backtrace:
In unknown file:
   ?: 19 [apply-smob/1 #<catch-closure 410f30>]
[..]
In gash/shell.scm:
 165: 1 [sh:exec-let () "./conftest" "triplet"]
In unknown file:
   ?: 0 [execle "./conftest" # "./conftest" ...]

ERROR: In procedure execle:
ERROR: In procedure execle: No such file or directory

Greetings,
Janneke

-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
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