kern/55076: lib/libc/sys/t_ptrace_wait*:access_regs_set_unaligned_pc_0x7 tests fail

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

>Number:         55076
>Category:       kern
>Synopsis:       lib/libc/sys/t_ptrace_wait*:access_regs_set_unaligned_pc_0x7 tests fail
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Mar 17 08:00:01 +0000 2020
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current
>Organization:
>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

Test cases matching the pattern

  lib/libc/sys/t_ptrace_wait*:access_regs_set_unaligned_pc_0x7

have been failing sporadically on the qemu-based TNF i386 testbed for
some time, and have now also started failing frequently on real amd64
hardware since around the time of this commit:

  2020.03.14.13.50.46 ad src/sys/arch/x86/acpi/acpi_cpu_md.c 1.82

Logs at:

  http://www.gson.org/netbsd/bugs/build/amd64-baremetal/commits-2020.03.html#2020.03.14.13.50.46

>How-To-Repeat:

>Fix: