"cabal exec hadrian" occasionally segfaults on aarch64

See failure history here: https://grafana.gitlab.haskell.org/d/167r9v6nk/ci-spurious-failures?orgId=2&var-types=cabal_hadrian_segfault&var-jobs=All&var-runners=All&from=now-30d&to=now&refresh=15m

Running hadrian/build-cabal --flavour=validate -j8 --broken-test= --bignum=gmp test --test-root-dirs=testsuite/tests/stage1 --test-compiler=stage1 runtest.opts+=...
[...]
hadrian/build-cabal: line 36: 120399 Segmentation fault      (core dumped) "$CABAL" --project-file="$PROJ" new-exec "${CABFLAGS[@]}" hadrian -- --directory "$PWD" "$@"
hadrian/build-cabal --flavour=validate -j8 --broken-test= --bignum=gmp test --test-root-dirs=testsuite/tests/stage1 --test-compiler=stage1 runtest.opts+= failed
error: hadrian stage1 test

Cheng suggests that it's probably cabal exec that is segfaulting.