reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git/commit/?id=52f690d7b6f55b7a18bddfeaf80d002dde83acbb
        git remote add tglx-devel https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git
        git fetch --no-tags tglx-devel timers/posix
        git checkout 52f690d7b6f55b7a18bddfeaf80d002dde83acbb
        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