Installworld: rescue/sh check failed, core dumped

From: bob prohaska <fbsd_at_www.zefox.net>
Date: Mon, 02 Jun 2025 19:01:37 UTC 
A pair of Pi2 (armv7) hosts running current have refused to
installworld after what looks like successful buildworlds. 

The tail of buildworld's log file reports:
make[1]: /usr/obj/usr/src/arm.armv7/toolchain-metadata.mk:1: Using cached toolchain metadata from build at www.zefox.org on Mon Jun  2 10:13:09 PDT 2025
--- __installcheck_UGID ---
--- __installcheck_sh_check ---
Bad system call (core dumped)
rescue/sh check failed, installation aborted

The two hosts have been successfully building and installing world/kernel
for some months. This error is new to me, if it's self-inflicted please
tell me what I did wrong. Git pull finds no updates that look related.

Thanks for reading

bob prohaska