reproduce (this is a W=1 build):
        git remote add trondmy-nfs git://git.linux-nfs.org/projects/trondmy/linux-nfs.git
        git fetch trondmy-nfs linux-next
        git checkout trondmy-nfs/linux-next
        b4 shazam https://lore.kernel.org/r/a25b8ee2-46c2-4468-8ebd-edbc40fc7417@gmail.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 net/sunrpc/xprtrdma/