reproduce (this is a W=1 build):
        git remote add rcu https://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux.git
        git fetch rcu rcu/dev
        git checkout rcu/rcu/dev
        b4 shazam https://lore.kernel.org/r/20250619175335.2905836-1-joelagnelf@nvidia.com
        # 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 kernel/rcu/