dbg: stray system stack error #12842

Job	Run time
ruby-bench (--warmup=1 --bench=1 --excludes=shipit)	14m 57s
make (check, --disable-yjit)	7m 18s
make (check, --enable-shared --enable-load-relative)	7m 15s
make (test-bundled-gems)	13m 5s
make (check, cppflags=-DVM_CHECK_MODE)	8m 27s
make (check, ubuntu-24.04, capi)	9m 27s
make (check, i686)	11m 23s
make (test-bundler-parallel, 50)	20m 59s
make-ibm	-1s
Ubuntu result	3s
	1h 32m 53s

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