reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git/commit/?id=9904eadec6dab60ab590fa800fccfc9715020e46
        git remote add hyperv https://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git
        git fetch --no-tags hyperv hyperv-fixes
        git checkout 9904eadec6dab60ab590fa800fccfc9715020e46
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash