reproduce:
        # https://github.com/frank-w/BPI-R2-4.14/commit/60b08ce2a46db43df611883b23db830b26fbedc2
        git remote add frank-w-bpi-r2-4.14 https://github.com/frank-w/BPI-R2-4.14
        git fetch --no-tags frank-w-bpi-r2-4.14 6.9-r4-mt76
        git checkout 60b08ce2a46db43df611883b23db830b26fbedc2
        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