workaround Clang v15 AArch64 miscompile that affects parallel collection #352

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	30m 18s
ci (a6osx, macos-12)	14m 36s
ci (ta6osx, macos-12)	18m 12s
ci (arm64osx, macos-14)	8m 15s
ci (tarm64osx, macos-14)	10m 28s
ci (i3le, ubuntu-22.04)	11m 15s
ci (ti3le, ubuntu-22.04)	14m 35s
ci (a6le, ubuntu-22.04)	8m 57s
ci (ta6le, ubuntu-22.04, CFLAGS+=-std=gnu89)	12m 0s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 25s
ci (i3nt, windows-2022, vs)	11m 11s
ci (ti3nt, windows-2022, vs)	14m 4s
ci (a6nt, windows-2022, vs)	12m 12s
ci (ta6nt, windows-2022, vs)	14m 34s
ci (ta6nt, windows-2022, gcc, CFLAGS+=-std=gnu89)	13m 43s
	3h 22m 45s

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