reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git/commit/?id=ca8adafcfc2495705fd11c9503894c6cbd05fc2c
        git remote add namhyung-perf https://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
        git fetch --no-tags namhyung-perf perf/hwmon-pmu
        git checkout ca8adafcfc2495705fd11c9503894c6cbd05fc2c
        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