Installer for 1.4.0

[Mathieu Othacehe]

Hello,

The installer has been hardened during the past months when it comes to
error reporting:

- Guile exceptions are caught, displayed and possibly uploaded to
  dump.guix.gnu.org if the user agrees to do so.

- Failing system commands can be run again.

I think that it would be nice to go a bit further as people tend to use
the stable Guix installer image and given our current release rate, the
future 1.4.0 could last for long.

It would be awesome if we could tackle the following issues before the
release:

- Guile and library segfaults could be reported as proposed here:
  https://issues.guix.gnu.org/58733.

- There is a nasty finalizer bug that has probably bitten a lot of users
  here: https://issues.guix.gnu.org/58732.

- The backtrace page is not displayed correctly if an exception occurs
  withing the final PTY: https://issues.guix.gnu.org/58734. This one is
  maybe not as important but it would be great to have it fixed so that
  every part of the installer is well covered by the dump mechanism.

- Displaying upfront that the WiFi, video card or any other hardware
  won't be supported by the installer/linux-libre in the spirit of:
  https://issues.guix.gnu.org/58549 would be great.

  For instance, I tested recently the installer on a laptop with an
  unsupported WiFi card. The WiFi page is skipped altogether by the
  installer which forces the user to plug an ethernet cable without
  explaining why. I think we could be a bit more didactic.

Any volunteers?

Thanks,

Mathieu