reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/broonie/ci.git/commit/?id=45552542703cbd042bfdd3fe8584bd42fd0d5d7b
        git remote add broonie-ci https://git.kernel.org/pub/scm/linux/kernel/git/broonie/ci.git
        git fetch --no-tags broonie-ci kselftest-mitigate-gnu-source
        git checkout 45552542703cbd042bfdd3fe8584bd42fd0d5d7b
        make W=1 O=/tmp/kselftest headers
        make W=1 O=/tmp/kselftest -C tools/testing/selftests
        make W=1 O=/tmp/kselftest -C tools/testing/selftests/bpf