bitcoin: arm64 CI failure

arm64 CI is failing with:

FAIL: minisketch/test
=====================

../build-aux/test-driver: line 109: ./minisketch/test: cannot execute binary file: Exec format error
FAIL minisketch/test (exit status: 126)

FAIL: univalue/test/object
==========================

../build-aux/test-driver: line 109: ./univalue/test/object: cannot execute binary file: Exec format error
FAIL univalue/test/object (exit status: 126)

FAIL: univalue/test/unitester
=============================

../build-aux/test-driver: line 109: ./univalue/test/unitester: cannot execute binary file: Exec format error
FAIL univalue/test/unitester (exit status: 126)

FAIL: qt/test/test_bitcoin-qt
=============================

../build-aux/test-driver: line 109: ./qt/test/test_bitcoin-qt: cannot execute binary file: Exec format error
FAIL qt/test/test_bitcoin-qt (exit status: 126)

See eg https://github.com/bitcoin/bitcoin/pull/27647/checks?check_run_id=14232303009 or https://github.com/bitcoin/bitcoin/pull/27746/checks?check_run_id=14231876127

I tried re-running the arm64 task for #27675 which had succeeded yesterday, and it now fails too (before vs after), which suggests either that the bug was introduced after commit fbe48f97dfec3138b06b5f00b75655da0c985008 up to commit 427853ab49f610e971b73ea4cc1d5366747e52b1 (nothing seemed likely to break minisketch/test there) or is an infrastructure issue (bad cache or bad hardware?).