toolchain/54703: GCC 8 breaks i386 floppy install

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         54703
>Category:       toolchain
>Synopsis:       GCC 8 breaks i386 floppy install
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Nov 17 12:35:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date => 2019.11.16.10.22.20
>Organization:
>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

Since the commit

  2019.11.16.10.22.20 mrg src/share/mk/bsd.own.mk 1.1161

with the commit message "i386 -> GCC 8.", the TNF i386 testbed is
failing at the stage where it attempts to boot the INSTALL kernel in
qemu from virtual floppies.  Where the last working version printed
the message

  Please remove disk 1, insert disk 2, and press return...

versions built with GCC 8 instead print

  Please remove disk 1, insert disk 0, and press return...

and things go downhill from there.

>How-To-Repeat:

Inspect the logs at

  http://releng.netbsd.org/b5reports/i386/commits-2019.11.html#2019.11.16.10.22.20

or point "anita install" at a recent enough -current/i386 build.

>Fix: