bin/54649: Many asan tests now fail on amd64

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

>Number:         54649
>Category:       bin
>Synopsis:       Many asan tests now fail on amd64
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Oct 25 17:15:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2019.10.23.00.06.07
>Organization:
>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

About 30 asan tests are failing on amd64 after these commits:

   2019.10.22.13.49.30 christos src/share/mk/bsd.own.mk 1.1157
   2019.10.22.18.43.14 aymeric src/sys/arch/arm/dts/socfpga_cyclone5_de0_nano_soc.dts 1.3
   2019.10.22.21.40.10 tnn src/sys/dev/ic/ssdfbvar.h 1.3
   2019.10.22.21.41.01 tnn src/sys/dev/ic/ssdfb.c 1.7
   2019.10.22.22.03.27 tnn src/sys/dev/ic/ssdfb.c 1.8
   2019.10.22.22.03.27 tnn src/sys/dev/ic/ssdfbvar.h 1.4
   2019.10.23.00.06.07 kamil xsrc/external/mit/xedit/dist/lisp/pathname.c 1.2

The first one in the list looks like the prime suspect.

Logs from real hardware:

  http://www.gson.org/netbsd/bugs/build/amd64-baremetal/2019/2019.10.23.00.06.07/test.html#failed-tcs-summary

>How-To-Repeat:

>Fix: