port-sparc64/59291: releng testbed: intermittent install failures

[campbell+netbsd%mumble.net@localhost]

>Number:         59291
>Category:       port-sparc64
>Synopsis:       releng testbed: intermittent install failures
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-sparc64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Apr 13 18:45:00 +0000 2025
>Originator:     Taylor R Campbell
>Release:        
>Organization:
The SparcBSD Intermittentestation
>Environment:
>Description:
The sparc64 releng testbed on anita (chronicled at https://releng.netbsd.org/b5reports/sparc64/) has had intermittent install failures for a long time:

https://releng.netbsd.org/b5reports/sparc64/2024/2024.01.11.04.45.20/install.log
https://releng.netbsd.org/b5reports/sparc64/2025/2025.01.03.06.32.22/test.log
https://releng.netbsd.org/b5reports/sparc64/2025/2025.02.09.10.27.29/install.log
https://releng.netbsd.org/b5reports/sparc64/2025/2025.03.06.01.14.51/install.log
https://releng.netbsd.org/b5reports/sparc64/2025/2025.04.13.09.44.58/install.log

Some of these failures report timecounter-went-backwards (by <1sec) around the end of the log, but not all of them.

These intermittent installation timeouts have been happening persistently for long enough that I doubt they reflect transient bugs introduced and fixed over time.
>How-To-Repeat:
anita test sparc64, probably
>Fix:
Yes, please!