Revert "qemu: upgrade to 5.0.0"

This reverts commit ba7ed3642fa5e15fe0eeca322a1baabd149ef6e7.

Reason for revert: breaking non-SDK VMs; see https://crbug.com/1114204

Original change's description:
> qemu: upgrade to 5.0.0
>
> Among other things, it fixes some bugs w.r.t. symlink loops in the '-L'
> option:
>
>   https://git.qemu.org/?p=qemu.git;a=commit;h=f3a8bdc1d5b260d31422edd46360ff849dfbcc93
>   util/path: Do not cache all filenames at startup
>
> Retain 'flag-o-matic' (not present upstream) because our bashrc hooks
> try to use it.
>
> BUG=chromium:1099508
> TEST=build; run ARM unit tests for various packages
>
> Cq-Depend: chromium:2278831, chromium:2284214
> Change-Id: Id243a4c90d379dc9221ed16a36744a949f60c253
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2278490
> Tested-by: Brian Norris <briannorris@chromium.org>
> Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
> Reviewed-by: Mike Frysinger <vapier@chromium.org>
> Commit-Queue: Manoj Gupta <manojgupta@chromium.org>

Bug: chromium:1099508, chromium:1114204
Cq-Depend: chromium:2278831
Change-Id: I63bebdd7ce3ae6ab012b987c35f7232c2596d9f6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2343463
Commit-Queue: Brian Norris <briannorris@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
10 files changed